'Nid iaith fain mohoni' : y Gymraeg ym Mangor a Chaernarfon yn ystod y bedwaredd ganrif ar bymtheg by Gwenfair Parry. ISBN 0947531661. Published by Canolfan Uwchefrydiau Cymreig a Cheltaidd Prifysgol Cymru in 2002. Publication and catalogue information, links to buy online and reader comments.