Adams, Henry
Houghton Miffiln, 1918
Buku Teks
Lawson, Henry, 1867-1922, author
John Ferguson, 1979
Buku Teks
Newman, William M.
McGraw-Hill, 1987
Buku Teks
Newman, Philip C.
Frederick A. Praeger, Inc , 1956
Buku Teks
US News and World Report, 1971
Buku Teks