This textbook is the one I kept after the course ended for reference.
Feudal Kingdom of England, 1042-1216, Paperback by Barlow, Frank, Brand New, …
This textbook was recommended by my instructor for the advanced module.
Pope Innocent Iii (1160/61-1216): To Root Up And To Plant
You will find that this textbook has a handy index of symbols and abbreviations.
THE FEUDAL KINGDOM OF ENGLAND, 1042-1216 (5TH EDITION) By Frank Barlow **Mint**
A nice touch in this textbook is the online access code included with purchase.
The Feudal Kingdom of England 1042-1216 by Barlow, Frank Paperback / softback
You will find that this textbook has a sturdy hardcover that resists wear.
POPE INNOCENT III (1160/61-1216): TO ROOT UP AND TO PLANT By John C. Moore *NEW*
What stands out about this textbook is the number of illustrations and diagrams.
The Feudal Kingdom of England, 1042-1216 (5th Edition) By Frank
A nice touch in this textbook is the online access code included with purchase.
The Feudal Kingdom of England, 1042-1216 (5th Edition), Barlow, Frank, 978058238
This textbook covers everything from the fundamentals to more specialized topics.
The Feudal Kingdom of England 1042-1216 by Barlow, Frank 0582381177 The Fast
This textbook covers both theory and hands-on exercises in equal measure.
POPE INNOCENT III TO ROOT UP AND TO PLANT BOOK 1160/61-1216 JOHN C MOORE
A nice touch in this textbook is the quick reference cards inside the cover.

