P. F. Collier & Son Corporation, 1959 ; 1969
Buku Referensi
Grolier Enterprises Corp., 1995
Buku Teks
P. F. Collier & Son Corporation, 1959
Buku Teks
Charles W. Eliot, edited
P. F. Collier & Son Corporation, 1959 ; 1969
Buku Referensi
Burrow, J.A., author
BlackWell Publishing, 2004
Buku Teks