BooQs publisher data, 2010
Buku Referensi
edited by Steven Moorhead and Gordon Grice
Rockport Publisher, 1997
Buku Referensi
edited by Catherine Spellman
Actar, 2003
Buku Teks
Simonds, John Ormsbee
McGraw-Hill, 1961
Buku Teks
University of Pennsylvania Press, 2002
Buku Teks