Tambunan, Lukas Ronggur Hasiholan, author
Program Pascasarjana Universitas Indonesia, 2016
UI - Tesis (Membership)
Aldine Publishing Company, 1968
Buku Teks
Pye, Keith
Stanley Thornes , 1992
Buku Teks
Carter, Gwendolen M., author
Praeger, 1973
Buku Teks
Ball, Alan R., author
Macmillan, 1974
Buku Teks