Durrance, E.M.; Laming, D.J. (1982): . University of Exeter. ISBN 0-85989-247-6. Hunt, P.J.; Wills, G.L., red. (1977): , Exeter: Devon County Council ISBN 0-903849-19-4. Milton, Patricia (2006): . Chichester: Phillimore. ISBN 1-86077-401-6.