by Phillip J. Cooper [and others]
Harcourt, Brace, 1998
Buku Teks
Denhardt, Robert B.
Thomson, 2009
Buku Teks
Denhardt, Robert B.
Harcourt College, 1999
Buku Teks
edited by David Fairman, Diana Chigas, Elizabeth McClintock and Nick Drager
Springer, 2012
eBooks
Herring, E. Pendleton
McGraw-Hill, 1936
Buku Teks