Unesco-UNEP International Environmental Education Programme & Hungerford, H. R. (1989). A prototype environmental education curriculum for the middle school: A discussion guide for Unesco training seminars on environmental education. Unesco.
Παραπομπή σε μορφή Chicago (17η εκδ.)Unesco-UNEP International Environmental Education Programme και Harold R. Hungerford. A Prototype Environmental Education Curriculum for the Middle School: A Discussion Guide for Unesco Training Seminars on Environmental Education. Paris: Unesco, 1989.
Παραπομπή σε μορφή MLA (9th εκδ.)Unesco-UNEP International Environmental Education Programme και Harold R. Hungerford. A Prototype Environmental Education Curriculum for the Middle School: A Discussion Guide for Unesco Training Seminars on Environmental Education. Unesco, 1989.