May, John D.
Duxbury Press, 1972
Buku Teks
Robson, William Alexander, 1895-1980, author
Stevens & Sons Limited, 1951
Buku Teks
Srivastava, G.P., author
Chand , 1965
Buku Teks
Kaufman, Herbert
John Hopkins, 1960
Buku Teks
Leiserson, Avery
The University of Chicago Press, 1942
Buku Teks