ebrary, Inc, Kügler, F., Féry, C., & Vijver, R. F. H. E. v. d. (2009). Variation and gradience in phonetics and phonology. Mouton de Gruyter.

ebrary, Inc, Frank Kügler, Caroline Féry, and Ruben Florentius Hendricus Eduardus van de Vijver. Variation and Gradience in Phonetics and Phonology. New York, NY: Mouton de Gruyter, 2009.

ebrary, Inc, et al. Variation and Gradience in Phonetics and Phonology. Mouton de Gruyter, 2009.