Lenk, John D., author
Reston , 1978
Buku Referensi
Thomas, Harry E., author
Prentice-Hall, 1965
Buku Referensi
Kaufman, Milton
McGraw-Hill, 1988
Buku Referensi
Middleton, Robert Gordon, 1908-, author
Reston Publishing, 1970
Buku Referensi
Hibberd, R. G.
McGraw-Hill, 1969
Buku Teks