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
Gellhorn, Walter, author
Macmillan, 1961
Buku Teks
U.S. Goverment, 2003
Buku Teks