Berlin Hodder and Stoughton 1966
Buku Referensi
Clarendon Press , 1995
Buku Referensi
Williams, Edwin B., author
Holt, Rinehart and Winston, [Date of publication not identified]
Buku Referensi
Treviño, Rose Zertuche, author
[American Management Association, ], 2009
eBooks
Castillo, Carlos, 1889-1967, compiler
The University of Chicago Press, 1948
Buku Referensi