Environmental Education Project (Portland, Or.). (1978). Clearing. Environmental Education Project.
Chicago-referens (17:e uppl.)Environmental Education Project (Portland, Or.). Clearing. Portland, Or.: Environmental Education Project, 1978.
MLA-referens (9:e uppl.)Environmental Education Project (Portland, Or.). Clearing. Environmental Education Project, 1978.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.