Happold, F.C.
Christophers, 1938
Buku Klasik
Brinton, Crane, 1898-1968
Prentice-Hall, 1957
Buku Teks
Robenso, James Harvey
Ginn , 1931
Buku Teks
Walker. Charles R.
McGraw-Hill, 1962
Buku Teks
Roe, Frederick William
Harcourt, Brace and Company, 1928
Buku Teks