Pounds, Norman J. G.
Frederick A. Praeger, 1964
Buku Teks
Selmann, R. R.
Edward Arnold, 1953
Buku Referensi
Sellman, Roger Raymond
Edward Arnold, 1954
Buku Referensi
Hazard, Harry W.
Princeton University Press, 1951
Buku Referensi
McEvery, Colin
Facts On File, 1979
Buku Referensi