Perkins, John, author
Berrett-Kochler, 2004
Buku Teks
Brown, Paul L.
Ronald Press Co , 1953
Buku Teks
Ross, Helen S.
Mayfield Publ., 1980
Buku Teks
Niven, Paul R., author
John Wiley & Sons, 2003
Buku Teks
Wendt, Paul F.
The University of California, 1966
Buku Teks