* Strong, Douglas H. ''Dreamers & Defenders: American Conservationists.'' (1988) [http://www.questia.com/PM.qst?a=o&d=8516594 online edition], good biographical studies of the major leaders | * Strong, Douglas H. ''Dreamers & Defenders: American Conservationists.'' (1988) [http://www.questia.com/PM.qst?a=o&d=8516594 online edition], good biographical studies of the major leaders |