Philips, author
Chancellor Press, 1999
Buku Referensi
Selmann, R. R., author
Edward Arnold, 1953
Buku Referensi
London Chancellor Press 1999,
Buku Referensi
McNally, Rand, author
Rand McNally & Co, 1957
Buku Referensi
Beckingham, C.F.
Macmillan & Co., 1960
Buku Referensi