Dvornik, Francis (1962): . Rutgers University Press. ISBN 978-0-8135-0799-6. Curta, Florin (2001): . Cambridge University Press. ISBN 978-1-139-42888-0. Barford, Paul M. (2001): . Cornell University Press. ISBN 978-0-8014-3977-3. Vlasto, A. P. (1970): . CUP Archive. ISBN 978-0-521-07459-9.