Butler, E. M.
Beacon Press, 1935
Koleksi Publik
Asimov, Isaac, author
Doubleday, 1964
Buku Referensi
by Renzo Rossi
Macmillan, 1996
Buku Referensi
Burke, Lance B., author
[American Management Association;, ], 2004
eBooks
Bowra, C. M., author
Time-Life Books, 1965
Buku Teks