Bethke, E. G. (1969). Basic drawing for biology students. Charles C. Thomas.
Lua i Stíl Chicago (17ú heag.)Bethke, Emil G. Basic Drawing for Biology Students. Springfield, IL: Charles C. Thomas, 1969.
Lua MLA (9ú heag.)Bethke, Emil G. Basic Drawing for Biology Students. Charles C. Thomas, 1969.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.