International encyclopedia of linguistics; Volume 1
William Bright, editor-in-chief
Oxford University Press, 1992
 Buku Referensi
International encyclopedia of linguistics; Volume 2
William Bright, editor-in-chief
Oxford University Press, 1992
 Buku Referensi
International encyclopedia of linguistics : volume 3
William Bright, editor-in-chief
Oxford University Press, 1992
 Buku Referensi
The Encyclopedia Americana : the international reference work, volume 4
Americana Corporation, 1960
 Buku Referensi
International encyclopedia of the social sciences : volume 3 & 4
edited by David L. Sills
Macmillan and The Free Press, 1968
 Buku Referensi