Whittlesey, Charles R., author
Macmillan, 1969
Buku Teks
Whittlesey, Charles R., author
Macmillan, 1967
Buku Teks
Whittlesey, Charles R., author
Macmillan, 1954
Buku Teks
Culbertson, John M.
McGraw-Hill, 1972
Buku Teks
Ritter, Lawrence S., author
Basic Books, 1974
Buku Teks