Barnard, Alan
Cambridge University Press, 2011
Buku Teks
Pawson, Ivan G.
John Wiley & Sons, 1977
Buku Teks
Baradat, Leon P.
[publisher not identified], [date of publication not identified]
Buku Teks
Brace, C. Loring
Macmillan, 1969
Buku Teks
Milner, Richard
Facts On File, 1990
Buku Referensi