Beer, Samuel H.
Clarendon Press, 1957
Buku Teks
Backman, Jules
The Brookings Institution, 1943
Buku Teks
Tew, Brian
Melbourne University Press, 1956
Buku Teks SO
Tew, Brian
Melbourne University Press, 1956
Buku Teks SO
Viton, Albert
John Day Company, 1940
Buku Teks