Manley, John F., author
Macmillan, 1976
Buku Teks
Schmidt, Steffen W., author
Wadsworth, 2009
Buku Teks
by Susan Welch, John Gruhl, John Comer and Susan M. Rigdon
Wadsworth/Cengage learning, 2010
Buku Teks
Artikel Jurnal
Griffith, Ernest
Frederick A. Praeger, 1954
Buku Teks