Case, Karl E., author
Prentice-Hall, 2002
Buku Teks
Case, Karl E., author
Prentice-Hall, 1999
Buku Teks
Henderson, J. Vernon, author
Heath and Com, 1991
Buku Teks
edited by Kenneth G. Elzinga
Harper & Row, 1972
Buku Teks
Ferguson, C. E., author
Holt, Rinehart and Winston, 1962
Buku Teks