Παραπομπή σε μορφή APA (7η εκδ.)

Hart, R. D. An ecological systems conceptual framework for agricultural research and development.

Παραπομπή σε μορφή Chicago (17η εκδ.)

Hart, Robert D. An Ecological Systems Conceptual Framework for Agricultural Research and Development. [Date of publication not identified].

Παραπομπή σε μορφή MLA (9th εκδ.)

Hart, Robert D. An Ecological Systems Conceptual Framework for Agricultural Research and Development.