Crawford, Bartholow V.
Barnes & Noble, 1953
Buku Teks
Holland, Norman Norwood
Oxford Universiy Press, 1990
Buku Referensi
Eaglestone, Robert
Routledge , 2005
Buku Teks
edited by Clarence L. Barnhart
Appleton-Century-Crofts, 1956
Buku Referensi
Gultom, Samuel
Greenwood Press, 1987
Buku Referensi