Citazione Stile APA (7a Edizione)

(1994). Project learning tree: Environmental education activity guide (2nd.). Project Learning Tree.

Citazione stile Chigago Style (17a edizione)

Project Learning Tree: Environmental Education Activity Guide. 2nd. Washington: Project Learning Tree, 1994.

Citatione MLA (9a ed.)

Project Learning Tree: Environmental Education Activity Guide. 2nd. Project Learning Tree, 1994.