Sykes, Egerton
London, J.M. Dent and Sons
Buku Referensi
[publisher not identified], [date of publication not identified]
Buku Teks SO
Paxton, John
J.M. Dent & Sons, 1992
Buku Referensi
Browning, D.C.
J.M. Dent & Sons, 1951
Buku Referensi
Arnold-Baker, C.
J.M. Dent & Sons, 1954
Buku Teks SO