1992.6 ISBN 4-938-56831-4 ^ Callenbach, Ernest; Heddle, James. ""Ecotopia Then & Now," an interview with ErnestCallenbach". Retrieved 2013-04-06. ^ Timberg
Ghostarchive and the Wayback Machine: Callenbach, Ernest. “"Ecotopia Then & Now," an interview with ErnestCallenbach”. YouTube. 2013年4月6日閲覧。 ^ Grove (1995年)