@inbook {Ohala1989, title = {Sound Change is Drawn from a Pool of Synchronic Variation}, booktitle = {Language change: Contributions to the study of its causes}, year = {1989}, pages = {171{\textendash}198}, publisher = {Mouton de Gruyter}, organization = {Mouton de Gruyter}, address = {New York}, author = {Ohala, John J.}, editor = {Breivik, L. E. and Jahr, E. H.} }