Genn, Robert C.
Parker Publishing Company, 1977
Buku Referensi
Lenk, John D.
McGraw-Hill, 1995
Buku Referensi
Grolle, Carl G.
Parker Publishing Company, 1977
Buku Referensi
Lenk, John D.
McGraw-Hill, 1999
Buku Referensi
Lenk, John D.
Prentice-Hall, 1971
Buku Referensi