Gildersleeve, Thomas R.
Prentice-Hall, 1978
Buku Teks
Johari
Fakultas Kesehatan Masyarakat Universitas Indonesia, 2007
UI - Tesis Membership
Varsegi, Alex
Van Nostrand Reinhold, 1988
Buku Teks
Kendall, Kenneth E.
Prentice-Hall, 1992
Buku Teks
Hawryszkiewycz, Igor Titus
Prentice-Hall, 1994
Buku Teks SO