H. G. Richardson 
English Parliament in the Middle Ages [PDF ebook] 

The English Parliament in the Middle Ages is a collection of 26 essays written by historians H. G. Richardson and G. O. Sayles between 1925 and 1967. These essays — some collaborative, and some written individually by Richardson and Sayles — illuminate various aspects of English parliamentary history, beginning with the origins of parliament. Brought together with a foreword and additional notes by G. O. Sayles, this volume provides a comprehensive reference point for all scholars interested in medieval bureaucracy and the history of law.