Lewis, R. O. (1958). Soil conservation in the Philippines: Terminal report, February 15, 1956-February 1, 1958. United States Operations Mission to the Philippines.
Chicago-referens (17:e uppl.)Lewis, Ralph O. Soil Conservation in the Philippines: Terminal Report, February 15, 1956-February 1, 1958. [Manila]: United States Operations Mission to the Philippines, 1958.
MLA-referens (9:e uppl.)Lewis, Ralph O. Soil Conservation in the Philippines: Terminal Report, February 15, 1956-February 1, 1958. United States Operations Mission to the Philippines, 1958.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.