|
on Environmental Economics |
| By: | Finger, Robert; Gerwig, Claude N. |
| Abstract: | Site Specific Technologies (SST) can reduce environmental pollution caused by common agricultural practice. Using a case study for corn yields, we investigate the impact of climate change (CC) on profitability of SSTs. We find CC to increase spatial variability of soils with respect to optimal input application and yield variability. This leads, ceteris paribus, to higher incentives for SST adoption in the future. |
| Keywords: | Climate Change; Site Specific Technologies; Adaptation; Crop Production Function |
| JEL: | Q54 Q01 Q12 O13 O31 |
| Date: | 2007–09 |
| URL: | http://d.repec.org/n?u=RePEc:pra:mprapa:4792&r=env |
| By: | Deressa, Temesgen Tadesse |
| Abstract: | This study uses the Ricardian approach to analyze the impact of climate change on Ethiopian agriculture and to describe farmer adaptations to varying environmental factors. The study analyzes data from 11 of the country ' s 18 agro-ecological zones, representing more than 74 percent of the country, and survey of 1,000 farmers from 50 districts. Regressing of net revenue on climate, household, and soil variables show that these variables have a significant impact on the farmers ' net reven ue per hectare.The study carries out a marginal impact analysis of increasing temperature and changing precipitation across the four seasons. In addition, it examines the impact of uniform climate scenarios on farmers ' net revenue per hectare. Additionally, it analyzes the net revenue impact of predicted climate scenarios from three models for the years 2050 and 2100. In general, the results indicate that increasing temperature and decreasing precipitation are both damaging to Ethiopian agriculture. Although the analysis did not incorporate the carbon fertilization effect, the role of technology, or the change in prices for the future, significant information for policy-making can be extracted. |
| Keywords: | Environmental Economics & Policies,Climate Change,Crops & Crop Management Systems,Global Environment Facility,Common Property Resource Development |
| Date: | 2007–09–01 |
| URL: | http://d.repec.org/n?u=RePEc:wbk:wbrwps:4342&r=env |
| By: | Benno Torgler (Queensland University of Technology); Bruno S. Frey (CREMA, Institute for Empirical Research in Economics, University of Zurich and CESifo); Clevo Wilson (The School of Economics and FinanceT, Queensland University of Technology) |
| Abstract: | The paper investigates the relationship between pro-social norms and its implications for improved environmental outcomes, an area which has been neglected in the environmental economics literature. We provide empirical evidence, demonstrating a strong link between perceived environmental cooperation (reduced public littering) and increased voluntary environmental morale, using European Values Survey (EVS) data for 30 Western and Eastern European countries. The robust results suggest that environmental morale and perceived environmental cooperation, as well as identifying the factors that strengthen these relationships, potentially bring about better environmental outcomes. |
| Keywords: | Environmental Preferences, Environmental Morale, Conditional Cooperation, Pro-Social Behavior |
| JEL: | H26 H73 D64 |
| Date: | 2007–08 |
| URL: | http://d.repec.org/n?u=RePEc:fem:femwpa:2007.84&r=env |
| By: | Edwin van der Werf (Kiel Institute for the World Economy); Sjak Smulders (University of Calgary and Tilburg University) |
| Abstract: | We study how restricting CO2 emissions affects resource prices and depletion over time. We use a Hotelling-style model with two non-renewable fossil fuels that differ in their carbon content (e.g. coal and natural gas) and in addition are imperfect substitutes in final good production. We show that an economy facing a CO2 flow-constraint may substitute towards the relatively dirty input. As the economy tries to maximise output per unit of emissions it is not only carbon content that matters: productivity matters as well. With an announced constraint the economy first substitutes towards the less productive input such that more of the productive input is available when constrained. Preliminary empirical results suggest that it is cost-effective to substitute away from dirty coal to cleaner oil or gas, but to substitute from natural gas towards the dirtier input oil. |
| Keywords: | Climate Policy, Non-Renewable Resources, Input Substitution |
| JEL: | O13 Q31 Q43 |
| Date: | 2007–08 |
| URL: | http://d.repec.org/n?u=RePEc:fem:femwpa:2007.83&r=env |
| By: | Valentina Bosetti (Fondazione Eni Enrico Mattei); Carlo Carraro (Fondazione Eni Enrico Mattei, University of Venice, CEPR, CESifo and CMCC); Emanuele Massetti (Fondazione Eni Enrico Mattei, Catholic University of Milan and CMCC); Massimo Tavoni (Fondazione Eni Enrico Mattei, Catholic University of Milan and CMCC) |
| Abstract: | It is widely recognized that technological change has the potential to reduce GHG emissions without compromising economic growth; hence, any better understanding of the process of technological innovation is likely to increase our knowledge of mitigation possibilities and costs. This paper explores how international knowledge flows affect the dynamics of the domestic R&D sector and the main economic and environmental variables. The analysis is performed using WITCH, a dynamic regional model of the world economy, in which energy technical change is endogenous. The focus is on disembodied energy R&D international spillovers. The knowledge pool from which regions draw foreign ideas differs between High Income and Low Income countries. Absorption capacity is also endogenous in the model. The basic questions are as follows. Do knowledge spillovers enhance energy technological innovation in different regions of the world? Does the speed of innovation increase? Or do free-riding incentives prevail and international spillovers crowd out domestic R&D efforts? What is the role of domestic absorption capacity and of policies designed to enhance it? Do greenhouse gas stabilization costs drop in the presence of international technological spillovers? The new specification of the WITCH model presented in this paper enables us to answer these questions. Our analysis shows that international knowledge spillovers tend to increase free-riding incentives and decrease the investments in energy R&D. The strongest cuts in energy R&D investments are recorded among High Income countries, where international knowledge flows crowd out domestic R&D efforts. The overall domestic pool of knowledge, and thus total net GHG stabilization costs, remain largely unaffected. International spillovers, however, are also an important policy channel. We therefore analyze the implication of a policy mix in which climate policy is combined with a technology policy designed to enhance absorption capacity in developing countries. Significant positive impacts on the costs of stabilising GHG concentrations are singled out. Finally, a sensitivity analysis shows that High Income countries are more responsive than Low Income countries to changes in the parameters and thus suggests to focus additional empirical research efforts on the former. |
| Keywords: | Climate Policy, Energy R&D, International R&D Spillovers, Stabilization |
| JEL: | H0 H2 H3 |
| Date: | 2007–07 |
| URL: | http://d.repec.org/n?u=RePEc:fem:femwpa:2007.82&r=env |
| By: | Hattori, Keisuke |
| Abstract: | This paper investigates the welfare effects of international transfers of environmental technologies in open economies with international oligopoly and transboundary pollution, and shows that policy differentiation between the donor and the recipient countries and/or product differentiation between the donor and the recipient firms play a critical role in obtaining bilateral agreement on the transfer policy. The results come from the fact that the policy differentiation weakens the strategic relationships in environmental policy setting between governments and that the product differentiation weakens the strategic relationships in quantity choices between firms. |
| Keywords: | Technology Transfer; Environmental Tax; Oligopoly; Product Differentiation |
| JEL: | Q56 |
| Date: | 2007–09–05 |
| URL: | http://d.repec.org/n?u=RePEc:pra:mprapa:4777&r=env |
| By: | Ziesemer, Thomas (Maastricht University, UNU-MERIT); Kriechel, Ben (Maastricht University, ROA) |
| Abstract: | The Porter Hypothesis postulates that the costs of compliance with environmental standards may be offset by adoption of innovations they trigger. We model this hypothesis using a game of timing of technology adoption. We show that times of adoption are earlier the higher the non-adoption tax. The environmental tax turns the preemption game with low profits into a game with credible precommitment yielding high profits (pro-Porter). If there is a precommitment game without environmental taxes, the introduction of a tax leads to lower profits (anti-Porter). An evaluation of the empirical literature indicates that the Porter hypothesis holds even for profit-maximizing firms under multiple market imperfections such as imperfect competititon, X-inefficiency, and agency costs. These are more likely to be present in sectors with large firms. In many case studies that we evaluate, though, we detect an element of explicit or implicit subsidies for environmentally friendly behaviour, which is in line with Pigovian policies. |
| Keywords: | Environmental Policy, Strategic Trade Theory, Technology Adoption, Porter Hypothesis |
| JEL: | Q2 F1 H7 O3 |
| Date: | 2007 |
| URL: | http://d.repec.org/n?u=RePEc:dgr:unumer:2007024&r=env |
| By: | Sylvie Démurger (GATE CNRS); Yang Weiyong (University of International Business & Economics, Beijing, China); Hou Yuanzhao (Chinese Academy of Forestry, Beijing, China) |
| Abstract: | Using the latest forest inventory, this paper provides a comprehensive analysis of China’s forest sector by focusing on new forest trends, forest policy changes and challenges to achieve a sustainable forest management. We analyze the dynamics of forest resources and provide an impact assessment of forest policies on China’s forestry development over the last decades. Moreover, the analysis of the forest market highlights substantial disequilibria marked by a limited domestic supply potential and a growing demand for forest products satisfied by increasing imports. Internal and external solutions are explored and their implications for China and supplying countries are assessed. |
| Keywords: | China - Forest management - Forest resources |
| JEL: | O13 O53 Q23 Q28 |
| Date: | 2007–04 |
| URL: | http://d.repec.org/n?u=RePEc:gat:wpaper:0712&r=env |
| By: | Zilberman, David; Rajagopal, Deepak |
| Abstract: | The world is witnessing a sudden growth in production of biofuels, especially those suited for replacing oil like ethanol and biodiesel. This paper synthesizes what the environmental, economic, and policy literature predicts about the possible effects of these types of biofuels. Another motivation is to identify gaps in understanding and recommend areas for future work. The analysis finds three key conclusions. First, the current generation of biofuels, which is derived from food crops, is intensive in land, water, energy, and chemical inputs. Second, the environmental literature is dominated by a discussion of net carbon offset and net energy gain, while indicators relating to impact on human health, soil quality, biodiversity, water depletion, etc., have received much less attention. Third, there is a fast expanding economic and policy literature that analyzes the various effects of biofuels from both micro and macro perspectives, but there are several gaps. A bewildering array of policies - including energy, transportation, agricultural, trade, and environmental policies - is influencing the evolution of biofuels. But the policies and the level of subsidies do not reflect the marginal impact on welfare or the environment. In summary, all biofuels are not created equal. They exhibit considerable spatial and temporal heterogeneity in production. The impact of biofuels will also be heterogeneous, creating winners and losers. The findings of the paper suggest the importance of the role biomass plays in rural areas of developing countries. Furthermore, the use of biomass for producing fuel for cars can affect access to energy and fodder and not just access to food. |
| Keywords: | Energy Production and Transportation,Environmental Economics & Policies,Renewable Energy,Transport Economics Policy & Planning,Energy and Environment |
| Date: | 2007–09–01 |
| URL: | http://d.repec.org/n?u=RePEc:wbk:wbrwps:4341&r=env |
| By: | Sylvie Démurger (GATE CNRS); Martin Fournier (GATE CNRS); Yang Weiyong (University of International Business & Economics, Beijing, China) |
| Abstract: | This article illustrates the impact of changes related to market reforms and environmental policies on the economic structure in rural China by providing a comparative analysis of several villages in a poor township in Beijing municipality. Two main concomitant phenomena are affecting agricultural and non-agricultural choices in the studied area. First, the introduction of market mechanisms is encouraging local population to engage in new activities that are closer to local comparative advantages. Second, rural households are facing new constraints in the form of environmental protection measures, which have weakened traditional insurance channels provided by forest resources and cattle stock. Drawing on household-level survey data and interviews with village heads conducted in ten villages of Labagoumen township in December 2003, this article analyzes households decisions in response to market reforms and environmental constraints. We find large disparities both between villages and households in the diversification process and discuss the reasons of observed inertia in the region, most households still heavily relying on corn production. |
| Keywords: | agrarian change, Environmental protection, Income-source diversification, rural China |
| JEL: | O18 O53 Q10 R20 |
| Date: | 2007–04 |
| URL: | http://d.repec.org/n?u=RePEc:gat:wpaper:0711&r=env |
| By: | Stuart Whitten; Shahbaz Khan; D. Collins; D. Robinson; John Ward (CSIRO Sustainable Ecosystems, Australia) |
| Abstract: | Irrigated agriculture often leads to recharge to local and regional groundwater systems greater than what the systems can absorb, resulting in the development of shallow watertables causing salinity and waterlogging. Policy based on emissions trading offers one option for effective management of existing recharge externalities if effective property rights to diffuse emissions can be defined. In this paper we combine the conclusions drawn from biophysical research with economic principles underpinning emissions trading to present such a system. Allocation of net recharge contracts to irrigation farms will internalize the costs associated with saline aquifer impacts. Irrigators may reduce their compliance costs by creating or purchasing credits that reduce recharge through perennial vegetation, engineering solutions or crop rotation options. We discuss the economic impacts of adopting such a policy in the Coleambally Irrigation Area in southwestern New South Wales, Australia. We also demonstrate some of the conclusions drawn from our research using experimental economics. |
| Keywords: | salinity, irrigation, recharge, tradeable emissions, cap and trade, hydrologic-economic modelling, experimental economics |
| JEL: | Q57 |
| Date: | 2007–09 |
| URL: | http://d.repec.org/n?u=RePEc:cse:wpaper:2007-07&r=env |
| By: | Giacomo D’Alisa |
| Abstract: | The spreading of the concept of sustainable development asks for a the definition of a sound common ground of the growing number of implementations. Here I propose a synopsis of the criticisms of the major methodological approaches to sustainability and point out the need, according to the ecocentric approaches, of a paradigm shift, from a linear to a systemic perspective, generally utilized in the thermodynamic and biological sciences. Starting from the systematization suggested by Turner, Pearce and Bateman (1996), which divide ustainability in technocentric and ecocentric, this paper shows that not all approaches consider growth always as the best solution to society problems. This implies that sustainability may be viewed as an intersection among the so-called economic, social and environmental pilasters of sustainable development. This work offers instead a concentric representation of it, whereby the environmental system contains the economic and social dimensions, since it represents the set of resources that allows dimensions’ functionality. A fourth institutional dimension, participatory democracy, should be added to obtain a complete visualization of sustainable development. |
| Keywords: | Sustainable approaches; Sustainable development; Economic growth; Technocentric approach; Ecocentric approaches; Entropy; Sustainability dimensions. |
| Date: | 2007–06 |
| URL: | http://d.repec.org/n?u=RePEc:ufg:qdsems:09-2007&r=env |
| By: | Pagiola, Stefano; Rios, Ana R.; Arcenas, Agustin |
| Abstract: | As the use of Payments for Environmental Services (PES) approaches in developing countries has grown, concern has arisen over the ability of poorer households to participate. This paper uses data from a PES project being implemented in Quindío, Colombia, to examine the extent to which poorer households that are eligible to participate are in fact able to do so. The project provides a strong test of the ability of poorer households to participate in a PES program as it requires participants to make substantial and complex land use changes. The results show that poorer households are in fact able to participate at levels that are broadly similar to those of better-off households. Moreover, their participation was not limited to the simpler, least expensive options. Transaction costs may be greater obstacles to the participation of poorer households than household-specific constraints. |
| Keywords: | Payments for Environmental Services (PES); poverty; silvopastoral; Colombia |
| JEL: | Q57 Q24 Q12 |
| Date: | 2007–09–06 |
| URL: | http://d.repec.org/n?u=RePEc:pra:mprapa:4794&r=env |
| By: | Stefan Baumgärtner (Centre for Sustainability, University of Lüneburg); Martin F. Quaas (Department of Ecological Modelling, UFZ-Centre for Environmental Research Leipzig-Halle) |
| Abstract: | Agro-biodiversity can provide natural insurance to risk averse farmers. We employ a conceptual ecological-economic model to analyze the choice of agrobiodiversity by risk averse farmers who have access to financial insurance. We study the implications for individually and socially optimal agro-ecosystem managementand policy design when on-farm agro-biodiversity, through ecosystem processes at higher hierarchical levels, generates a positive externality on other farmers. We show that for the individual farmer natural insurance from agro-biodiversty and financial insurance are substitutes. While an improved access to financial insurance leads to lower agro-biodiversity, the eects on the market failure problem (due to the external benefits of on-farm agro-biodiversity) and on welfare are determined by properties of the agro-ecosystem and agro-biodiversity’s external benefits. We derive a specific condition on agro-ecosystem functioning under which, if financial insurance becomes more accessible, welfare in the absence of regulation increases or decreases. |
| Keywords: | agro-biodiversity, ecosystem services, agro-ecosystem management, insurance, risk-aversion, uncertainty |
| JEL: | Q1 Q57 H23 D62 |
| Date: | 2007–09–12 |
| URL: | http://d.repec.org/n?u=RePEc:lue:wpaper:61&r=env |
| By: | Paunić, Alida |
| Abstract: | Strong more than doubled crude oil price rise from 2002 to 2007 brought significant profits to oil companies worldwide. Rising revenues, profits and increasing shareholders wealth are consequence of this favorable situation. Being non renewable resource, unequally distributed, responsible for many crises, wars, environmental pollutions, weapon trading, GDP fall, rising unemployment, interest rates and reaching its peak production point in the world of increasing gasoline demand, higher environmentally standards, global worming, natural catastrophes, constrained refining capacity forces us to ask: is the rising wealth to small number of shareholders only we should expect? Paper examines oil companies and their contribution to promote social developments, clean energy, behave as good tax subject , closely work with government and various institutions to advance environmentally friendly world. |
| Keywords: | energy; oil; non renewable |
| JEL: | Q40 Q30 |
| Date: | 2005–03–06 |
| URL: | http://d.repec.org/n?u=RePEc:pra:mprapa:4898&r=env |
| By: | Yang, H.; Pollitt, M. |
| Abstract: | In this article we examine the effects of undesirable outputs on the Malmquist TFP indices. Our empirical work uses an unbalanced panel which covers 796 utility and non-utility coal-fired power plants in China during 1996-2002. In order to meet the requirement of a balanced panel for calculating the Malmquist indices, an innovative fake unit approach has been introduced. Our final results show that (1) the growth of the Chinese electricity heavily depends upon an increase of resource input; and (2) huge potential remains with regards to the efficiency improvement and emissions control in Chinese coal-fired power plants. Key words: Malmquist indicies, total factor productivity, Chinese electricity, power plant efficiency. |
| JEL: | D24 L94 |
| Date: | 2007 |
| URL: | http://d.repec.org/n?u=RePEc:cam:camdae:0740&r=env |
| By: | Nathalie Rousset (LEPII - Laboratoire d'Economie de la Production et de l'Intégration Internationale - [CNRS : FRE2664] - [Université Pierre Mendès-France - Grenoble II]) |
| Abstract: | Le changement climatique fait peser de nombreux risques d’impacts en Chine. Les ressources en eau dans les plaines du nord pourraient être particulièrement affectées. Si les équilibres sont déjà souvent rompus dans cette région, le réchauffement attendu jouera un rôle d’accélérateur de dynamiques existantes d’aggravation des déficits hydriques. Dans le contexte de compétition intersectorielle pour l’allocation de l’eau qui se dessine, la production céréalière du nord de la Chine apparaît comme un secteur particulièrement vulnérable. La diminution attendue des rendements des principales cultures pose alors la question des stratégies d’adaptation qui pourraient être adoptées. Mise en place de manière anticipée, une politique de l’eau axée de manière structurelle sur la rareté de la ressource permettrait de réduire ces risques tout en répondant à des défis déjà sensibles. Les impacts résiduels pourraient cependant rester conséquents. L’ouverture commerciale et les possibilités d’importer de l’eau sous forme de produits agricoles ouvrent de nouvelles perspectives pour une utilisation plus efficace des ressources hydriques,à mettre en balance avec le principe d’autosuffisance alimentaire. |
| Keywords: | CHANGEMENT CLIMATIQUE ; ADAPTATION ; AGRICULTURE |
| Date: | 2007–09–06 |
| URL: | http://d.repec.org/n?u=RePEc:hal:papers:halshs-00170103_v1&r=env |
| By: | Katherine Kiel (Department of Economics, College of the Holy Cross; New England Public Policy Center, Federal Reserve Bank of Boston) |
| Abstract: | Federal, state and local wetlands protection laws that restrict landowners’ ability to develop their properties in certain ways could decrease the value of the affected properties. However, the regulations could also give benefits to nearby neighbors who no longer need worry about increased development in their area. Given that some properties may decline in value, while others increase, the impact on individual properties must be determined empirically. This study uses a data set from Newton, Massachusetts to examine the impact of wetlands laws on the regulated properties, as well as on proximate properties. Looking at house sales data from 1988 through 2005, the hedonic technique is used to estimate the effect of wetlands regulations on single family home prices and finds that having wetlands on a property decreases its value by 4% relative to non-regulated properties. Homes that are contiguous to regulated houses do not experience any change in price. Thus it seems unlikely that neighbors are receiving any benefit from knowing that further development is restricted in their immediate vicinity. |
| Keywords: | Environment, housing, amenities, hedonic pricing, wetlands |
| JEL: | Q51 Q53 R2 |
| Date: | 2007–09 |
| URL: | http://d.repec.org/n?u=RePEc:hcx:wpaper:0707&r=env |
| By: | Yang, H.; Pollitt, M. |
| Abstract: | Different from traditional efficiency research and previous studies considering undesirable outputs, this paper proposes models which distinguish weak and strong disposability features among various undesirable outputs based on the technical nature of the undesirable outputs. The paper illustrates the approach using a research sample covering 582 base-load Chinese coal-fired power plants in 2002. Our final results show that (1) imposing the technically correct disposability features on undesirable outputs makes a significant difference to the final efficiency evaluation. This suggests the necessity of properly distinguishing disposability features among undesirable outputs in efficiency models; (2) compared to their US and European counterparts, Chinese power plants relatively waste more resources. This suggests a great urgency for the Chinese electricity industry to improve its efficiency in coal-fired electricity generation sector. Key words: Economics: input-output analysis; Environment; Government: energy policies; Industries: electric; Statistics: nonparametric. |
| JEL: | D24 L94 |
| Date: | 2007 |
| URL: | http://d.repec.org/n?u=RePEc:cam:camdae:0741&r=env |
| By: | Franz Gatzweiler (Center for Development Research, University of Bonn, Walter-Flex-Str. 3, 53113 Bonn); Jörg Volkmann (Amber Foundation, Freiburg, Germany,) |
| Abstract: | This paper aims at explaining the importance of the democracy stance as compared to the efficiency stance in order to deal with complexity in biodiversity conservation. While the efficiency stance refers to the realm of relatively simple systems, individual rationality, and instrumental values, the complexity stance transcends these boundaries into the realm of complex systems, social rationality and intrinsic values. We argue that the task of biodiversity conservation is impossible to achieve in economically efficient ways, because (a) it is impossible to come to a (fully informed) complete account of all values, not only because it is costly but also because (b) moral values are involved which (by their nature) exclude themselves from being accounted for, and (c) biodiversity conservation can be regarded as an end in itself instead of only a means towards an end. The point we raise is, that in order to cope with biodiversity conservation we need to apply valuation methods which are from the complexity stance, take better account of intrinsic values and feelings, as well as consider social rationality. Economic valuation methods are themselves 'value articulating institutions' and as biodiversity conservation confronts us with the complexity of social-ecological systems, the choice of the 'value articulating institutions' needs to consider their ability to capture instrumental and intrinsic values of biodiversity. We demonstrate a method, based on cybernetics, which is able to take into account the issues raised. |
| Keywords: | Biodiversity conservation, efficiency, complexity, values, institutions |
| JEL: | B52 Q51 Q57 |
| Date: | 2007–08 |
| URL: | http://d.repec.org/n?u=RePEc:hah:icardp:1807&r=env |
| By: | Vicent Alcantara Escolano (Departament d'Economia Aplicada, Universitat Autonoma de Barcelona) |
| Abstract: | El objetivo de estas páginas, que es parte de una investigación más amplia, es el desarrollo de un primer análisis de las relaciones entre la estructura productiva de la economía española y las emisiones de CO2, el más importante de los gases de efecto invernadero, a la atmósfera. Después de exponer la metodología utilizada, que permite la utilización conjunta en análisis expost, como el que nos ocupa, de los multiplicadores de oferta y demanda, se obtienen resultados relevantes que permiten un estudio detallado de las mencionadas relaciones. Posteriormente se determinan los sectores |
| Keywords: | Input-output, emisiones de CO2, sectores clave en la emisión, multiplicadores de demanda y producción. |
| JEL: | C67 Q40 Q43 |
| Date: | 2007–07 |
| URL: | http://d.repec.org/n?u=RePEc:uab:wprdea:wpdea0702&r=env |
| By: | Arias Arbelaez, Fabio Alberto |
| Date: | 2006–12–03 |
| URL: | http://d.repec.org/n?u=RePEc:col:000149:003969&r=env |
| By: | Fabio A. Arias.; Carlos Andrés Pérez |
| Date: | 2006–09–03 |
| URL: | http://d.repec.org/n?u=RePEc:col:000149:003970&r=env |