Sommer, Robert
New York, 2002
Buku Teks
Kimmel, Allan J.
Blackwell Publishing, 2007
Buku Teks
Kerlinger, Fred Nichols, 1910-
CBS College Publishing, 1986
Buku Teks
edited by Khondkar E. Karim
Emerald, 2016
eBooks
Leavitt, Fred
C. Brown Publishers , 1991
Buku Teks