Cyhoeddwyd yn wreiddiol = Originally published: Cambridge: Cambridge University Press, 1979.
Y ddrama gyfoes : damcaniaethau ac arferion. Cyfrol 3, Mynegiadaeth a'r theatr epig by J. L. Styan. ISBN 9781843237716. Published by Gomer in 2007. Publication and catalogue information, links to buy online and reader comments.