Luthans, Fred
McGraw-Hill, 1981
Buku Teks
edited by James L. Jarrett and Sterling M. McMurrin
Henry Holt, 1954
Buku Teks SO
Gennifer Furst, editor
SAGE , 2009
Buku Teks
Hanes, Ernest
Macmillan, 1937
Buku Teks SO
Edited by Michael Huemer
Routledge, 2002
Buku Teks SO