Oxford University Press, 1971
Buku Referensi
Clarendon Press, 1994
Buku Referensi
Crawley, Angela, author
Oxford University Press, 1994
Buku Referensi
edited by Thomas M. Paikeday
Holt, Rinehart and Winston, 1976
Buku Referensi
Oxford university press , 1992
Buku Teks