Spear, Percival
University of Michigan Press, 1961
Buku Teks
Brown, Joe David
Time Incorporated, 1961
Buku Teks SO
Bradford, Frederick A.
Longman, Green, 1932
Buku Teks
Rodgers, Raymond
Alexander Hamiltion Institute, 1962
Buku Teks SO
Thorne, W.J.
Oxford University Press , 1948
Buku Teks