Michael Kalvius, Paul Kienle
Springer, 2012
eBooks
Hutchison, Bruce
Longmans Green, 1953
Buku Teks
Donaldson, Norman
Bowling Green University Popular Press, 1971
Buku Teks
Winston, Robert
BBC Worldwide Limited, 2004
Multimedia
Ueberroth, Peter
William Morrow, 1985
Buku Teks