Wilhite, Virgle Glenn
Bookman Associates , 1958
Buku Teks
Datta, Bhabatosh
Tata McGraw-Hill, 1978
Buku Teks
Seligman, Edwin R.A., author
Columbia University Press, 1949
Buku Teks
Hunt, E. K.
Harper & Row Pub., 1972
Buku Teks
Gray, Alexander, author
Longmans , 1959
Buku Teks