Salisbury, Harrison E.
Harrison, 1969
Buku Teks
Utley, Freda
The Bobbs-Merrill Company, 1947
Buku Teks
Callis, Helmut G.
Henry Holt and Company, 1959
Buku Teks
Moorad, George
E.P. Duttom, 1949
Buku Teks
Chu-Yuan, Cheng
Frederick A. Praeger, 1964
Buku Teks