出典: Barbara F.Grimes, ed., Ethnologue: Languages
of the World, 14th ed., CD.ROM version (Dallas, TX: SIL, 2000);
Michael Krauss,“The World's Languages in Crisis,” vol. 68,no.
1 (1992); Jonathon Knight,“Lost for Words,”New Scientist, 12
August 2000; Daniel Nettle and Suzanne Romaine, Vanishing Voices:
The Extinction of the World's Languages (New York: Oxford University
Press, 2000); Barbara Walcraff,“What Global Language,”The Atlantic
Monthly, November 2000; U.S. Census Bureau data, www.census.gov
and Worldwatch estimate.