Engelken, R., Engelken, R., & Slattery, P. (1981). The art of natural farming & gardening. Barrington Hall Press.
Lua i Stíl Chicago (17ú heag.)Engelken, Ralph, Rita Engelken, agus Pat Slattery. The Art of Natural Farming & Gardening. Greeley, Iowa: Barrington Hall Press, 1981.
Lua MLA (8ú heag.)Engelken, Ralph, et al. The Art of Natural Farming & Gardening. Barrington Hall Press, 1981.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.