By Jonathan Williams
By Roy, A. E., Clarke, D.
By Brian Martin
By G. Miller (President, Earth Education and Research)
By Peter H. Raven, Linda R. Berg
By Starr
By Earl Robert Babbie, Frederick S. Halley, William E. Wagner, Jeanne S. Zaino
By Hilary P.M. Winchester
By R.C. Weimer
By Rebecca J. Elliott (University of Utah, USA)
By J.C. Yates
By Geoff Der (University of Glasgow, Scotland, UK), Brian S. Everitt (King's College, University of London
By Serge Lang
By GAIER
By Herbert Goldstein, Charles Poole, John Safko
By Ron Larson (The Pennsylvania State University, The Behrend College)
By singh-kuldeep
By Paul DuChateau, D. W. Zachmann
By Schools Council
By Bernard Moret, Henry D. Shapiro
By David Butler
By Elliott, William H., Daphne C.
By Barry Render, Ralph M. Stair
By N. Nissanke
By John A. Dossey, Albert D. Otto, Lawrence E. Spence, Charles Vanden Eynden
By Bruno Dente
By Paul Newbold