Sayre, Wallace S., author
Barnes & Noble, 1964
Buku Teks
Posey, Rollin Bennett, author
Littlefield, Adam, 1958
Buku Teks
by Susan Welch ... [and others]
Thomson, 2006
Buku Teks
Wheare, K. C.
Oxford University Press, 1963
Buku Teks
Chapman, R.J.K., author
George Allen and Unwin, 1984
Buku Teks