Cass, James
New York, Harper & Row Publishers
Buku Referensi
Berkeley University of California Press 1968
Buku Teks
Frederick, Robert W.
USA Appleton 1947
Buku Teks
Jakarta: Depdikbud, 1999,
Buku Referensi
Universitas Indonesia
Jakarta: LP UI, 1990,
Buku Referensi