J. K. Chambers & Natalie Schilling 
Handbook of Language Variation and Change [PDF ebook] 

The Handbook of Language Variation and Change, written by a distinguished international roster of contributors, reflects the vitality and growth of the discipline in its multifaceted pursuits. It is a convenient, hand-held repository of the essential knowledge about the study of language variation and change. Written by internationally recognized experts in the field. Reflects the vitality and growth of the discipline. Discusses the ideas that drive the field and is illustrated with empirical studies. Includes explanatory introductions which set out the boundaries of the field and place each of the chapters into perspective.