Alfred Endres is Full Professor of Economics at the University of Hagen, Germany, and Permanent Visiting Professor of Environmental Economics at the University of Witten/Herdecke, Germany. He has also taught at the Technical University of Berlin, Zhejiang University at Hangzhou, China, and the State University of New York at Buffalo. He held visiting appointments at the University of Florida, the University of California, San Diego and La Trobe University, Melbourne. Alfred Endres is the author of 14 books on environmental economics, applied economics, and microeconomics. He is the author of numerous articles in journals such as the Canadian Journal of Economics, Energy Economics, Environmental and Resource Economics, Journal of Environmental Economics and Management, Journal of Industrial Economics, Public Choice as well as Social Choice and Welfare. The European Association of Environmental and Resource Economists published a special issue of its official journal, Environmental and Resource Economics, " in honour of Alfred Endres" (Part I: Vol. 62, No. 4 (Dec. 2015), Part II: Vol. 65, No. 1 (Sept. 2016)). Beyond his scientific activities, Endres performs as the lead singer of Trio Rockato, a regionally acclaimed rock band. Volker Radke is Professor of Economics at the Baden-Wuerttemberg Cooperative State University Ravensburg, Germany. He also taught at the University of Dortmund and the University of Hagen, both Germany. He published several books and articles in journals, especially on the topic of sustainable development and its indicators.