Bindoff, S.T., author
Penguin Books, 1951
Buku Teks
Lavell, C.F., author
Macmillan, 1919
Buku Teks
Compton, Charles, author
McGarw-Hill, 1979
Buku Teks
Downs, Anthony
Little, Brown and Co., 1967
Buku Teks
Gunther, John, 1901-1970, author
Harper & Brothers, 1942
Buku Teks