Lenk, John D., author
Prentice-Hall, 1983
Buku Referensi
Genn, Robert C., author
Parker Publishing Company, 1977
Buku Referensi
Lenk, John D., author
McGraw-Hill, 1999
Buku Referensi
Lenk, John D., author
Prentice-Hall, 1971
Buku Referensi
Robinson, Vester, author
Reston Publishing Company, 1974
Buku Referensi