books.google.co.uk - "During the Merovingian centuries when most kings were weak, and brutal men fought over power and booty, ordinary folk, as well as many who were not so ordinary, again found themselves in desperate need of protection. The result was the appearance and wide extension of a practice called commendation....http://books.google.co.uk/books/about/A_History_of_the_Middle_Ages.html?id=JDAJ5VFYQlUC&q=Frederick&utm_source=gb-gplus-shareA History of the Middle Ages
