Roe, F.C.
Longmans, Green , 1956
Buku Teks
Happold, F.C.
Christophers, 1938
Buku Klasik
Brinton, Crane, 1898-1968, author
Prentice-Hall, 1957
Buku Teks
Robenso, James Harvey
Ginn , 1931
Buku Teks
Walker. Charles R., author
McGraw-Hill, 1962
Buku Teks