Soegondo
Gadjah Mada University Press, 1993
Buku Teks
Comfort, Jeremy
Oxford University Press, 1994
Buku Teks SO
Smith, Jennifer
Macmillan, 1982
Buku Teks SO
Clynes, A.J.
International Development Program of Australian Universities, 1985
Buku Teks SO
Tilbury, Alex
Cambridge University Press , 2011
Buku Teks