Crystal, David, 1941-
Language death
Cambridge University Press, 2005
 Buku Teks SO
Crystal, David, 1941-
Language death
Cambridge University Press, 2004
 Buku Teks SO
Dalby, Andrew
Language in danger
A. Lane, 2002
 Buku Teks
Austin, Peter K.
The Cambridge handbook of endangered languages
Cambridge University Press, 2011
 eBooks
Thomas, David
Some Philippine language subgroupings : a lexicostatistical study / David Thomas and Alan Healey
[publisher not identified], 1962
 Buku Teks