Language change progress or decayn

Ngā taipitopito rārangi puna kōrero
Kaituhi matua:	Aitchison, Jean
Hōputu:	Pukapuka
Reo:	Ingarihi
I whakaputaina:	Bungay, Suffolk Fontana Paperbacks 1981.
Ngā marau:	Sociolinguistics. Historical linguistics.