Barus, Septalina Manullang, author
Fakultas Psikologi Universitas Indonesia, 2002
UI - Tesis (Membership)
Cavanagh, Michael E.
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Buku Teks
Andi Mappiare A.T.
RajaGrafindo Persada, 2006
Buku Teks
Hansen, James C., author
Allyn and Bacon , 1986
Buku Teks
Fenti Hikmawati, author
RajaGrafindo Persada, 2010
Buku Teks