Sources
     

'Yeavering, An Anglo-British centre of early Northumbria' by Brian Hope-Taylor published by HMSO (ISBN 011 670552 3) is the definitive work on the subject. It covers, in enormous and fascinating detail, the excavations carried out on the Ad Gefrin site in the late fifties and early sixties. Filled with detailed maps and diagrams the book gets the facts across but also manages to draw the reader into the excitement of discovery. A wealth of background historical information is presented too. The book forms No.7 in the Archaeological reports of the Department of the Environment.
 
The Northumberland National Park have produced a handy series of booklets and leaflets as a part of their 'Discovering our Hillfort Heritage' project. They are available from National Park centres, Tourist Information centres and can be found in some shops and libraries.