Walker, Warren F.
Saunders College Pub., 1986
Buku Referensi
William N. McFarland ...[et al.]
Macmillan, 1979
Buku Teks
Pough, F. Harvey, author
Prentice-Hall, 1996
Buku Teks
Pough, F. Harvey, author
Prentice-Hall, 1999
Buku Teks
Orr, Robert T., author
Saunders, 1976
Buku Teks