Cable, Raymond M., author
Burgess, 1958
Buku Teks
by Elmer R. Noble ... [and others]
Lea & Febiger, 1989
Buku Referensi
Roberts, Larry S.
McGraw-Hill, 2000
Buku Teks
Chandler, Asa C.
John Wiley & Sons, 1961
Buku Teks
Craig, Charles Franklin, author
Lea & Febiger, 1951
Buku Teks