Katzner, Kenneth, author
The languages of the world
Routledge, 1995
 Buku Referensi
The World's major languages
edited by Bernard Comrie
Oxford University Press, 1987
 Buku Teks
The World's major languages
edited by Bernard Comrie
Routledge, 1991
 Buku Referensi
Campbell, George L., author
Concise compendium of the world's languages
Routledge, 1995
 Buku Referensi
Campbell, George L., author
Concise compendium of the worlds languages
Routledge, 1998
 Buku Teks