Johnston, R.J. (Ronald John)
Longman, 1978
Buku Teks
David J. Bartholomew ... [et.al]
CRC Press, Taylor & Francis Group, 2008
Buku Teks
Universitas Indonesia, 2006
UI - Skripsi (Membership)
Heumann, Christian
Springer International Publishing, 2016
eBooks
Forthofer, Ron N.
Lifetime Learning Publications, 1981
Buku Teks