Bernd Heine & Elizabeth Closs Traugott 
Approaches to Grammaticalization [PDF ebook] 
Volume I. Theoretical and methodological issues

The study of grammaticalization raises a number of fundamental theoretical issues pertaining to the relation of langue and parole, creativity and automatic coding, synchrony and diachrony, categoriality and continua, typological characteristics and language-specific forms, etc., and therefore challenges some of the basic tenets of twentieth century linguistics.This two-volume work presents a number of diverse theoretical viewpoints on grammaticalization and gives insights into the genesis, development, and organization of grammatical categories in a number of language world-wide, with particular attention to morphosyntactic and semantic-pragmatic issues.
The papers in Volume I are divided into two sections, the first concerned with general method, and the second with issues of directionality. Those in Volume II are divided into five sections: verbal structure, argument structure, subordination, modality, and multiple paths of grammaticalization.