Crampton, Richard, author
Routledge, 1996
Buku Referensi
edited by John Odmark
John Benjamins B.V. , 1979/1980/1981/1982
Buku Teks SO
edited by Maggie Toy
Academy Editions, 1996
Buku Teks SO
Hertzman, Clyde
DC The International Bank for Reconstruction and Development , 1995
Buku Teks
edited by Geoffrey A. Hosking and George F. Cushing
Macmillan Press, 1989
Buku Teks