Baxter, Martin
Cambridge university press, 1996
Buku Teks
Gisela
Universitas Indonesia, 2016
UI - Skripsi Membership
Lewis, Nigel C.
Thomas Telfors, 1994
Buku Teks
Langsam, Yedidyah
Prentice-Hall, 1996
Buku Teks
Means, Gardiner C.
Harper & Brothers Publishers, 1962
Buku Teks