Wagener, Albert M.
D. Van Nostrand Company, Inc., 1950
Buku Teks
Lower, Arthur R.M.
Longmans, Green and Company, 1959
Buku Teks
Lower, Arthur R.M.
Longmans, Green and Company, 1958
Buku Teks
Haynes, R.M.
Gower Publ., 1985
Buku Teks
Younger, R. M.
Rigby, 1975
Buku Teks