Keffer, C. A. (1907). Nature studies on the farm: Soils and plants. American Book Co..
Lua i Stíl Chicago (17ú heag.)Keffer, Charles A. Nature Studies on the Farm: Soils and Plants. New York: American Book Co., 1907.
Lua MLA (8ú heag.)Keffer, Charles A. Nature Studies on the Farm: Soils and Plants. American Book Co., 1907.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.