The Habibie Center,
Majalah, Jurnal, Buletin
Arnold, H.J.P.
Dufour Editions, 1966
Buku Teks
edited by Peter Mansfield
Oxford University Press, 1973]
Buku Teks SO
Halm, George N.
Feffer and Simons, 1968
Buku Teks
Senelle, Robert
Ministry of Foreign Affairs and External Trade, 1979
Buku Teks SO