edited by L.G. Whitby and Walter Lutz
Churchill Livingstone, 1971
Buku Referensi
Barker, D.J.P.
Churchil Livingstone, 1976
Buku Teks SO
by James J. Nora [and others]
[Publisher not identified], [Date of publication not identified]
Buku Teks
James J. Nora [and others]
Lea & Febiger , 1993
Buku Teks SO
Tulloch, Mitch
Currency Press, 1986
Buku Teks SO