Frison-Roche, Roger
Bruxelles Zurich Monreal, 1981
Buku Teks
Lambirth, Andrew
Learning Matters, 2005
Buku Teks SO
edited by John L. Bradley and Martin Stevens
Rinehart and Winston, 1968
Buku Teks
Weston, Martin
Oxford, 1991
Buku Teks
Nelson, Andrew Nathaniel
Charles E . Tuttle, 1966 ; 1986
Buku Referensi