Reuven Y. Hazan 
Cohesion and Discipline in Legislatures [PDF ebook] 

The existence of noticeable ‘unified’ parties is central to the theory and practice of democracy in general, and to parliamentary democracy in particular. However, legislative studies scholars have good reason to cease treating parties as monolithic, unitary actors, for they evidently are not. The first step in this direction is to ask why one of t