Levison, Arnold B.
Pegasus, 1974
Buku Teks
Beckerman, Andrew P., author
Oxford University Press, 2017
eBooks
Klein, Lawrence R., author
Prentice Hall of India, 1969
Buku Teks
Arnold, Von Robert
Pradnya Paramita, 1987"
Buku Teks
Smith, Carry D.
Boston Houghton Mifflin Co 1985,
Buku Teks