edited by Geoffrey Barraclough
Times Books, 1984
Buku Referensi
Published for Newsweek by Funk & Wagnalls, 1950
Buku Teks SO
Turnbull, C.M. (Constance Mary)
Oxford University Press, 1985
Buku Teks SO
Powell, Robert
Periplus, 2004
Buku Teks SO
Vinache, Harold M.
George Allen and Unwin, 1950
Buku Teks SO