B. S. Chlepner
The Bookings Institution, 1943
Buku Teks
Thorne, W.J., author
Oxford University Press , 1948
Buku Teks
Bradford, Frederick A., author
Longmans, Green, 1932
Buku Teks
edited by Benyamin Haggott Beckhart
Columbia Universary Press, 1954, 1956
Buku Teks
Basu, S.K.
Macmillan Press, 1974
Buku Teks