1. The Brachiopod Zonal Indices of the Stages Costonian to Onnian in Britain;Bancroft;Palaeont,1945
2. The Stratigraphy of the Bala district, Merionethshire;Bassett;Q. J. geol. Soc. Lond.,1966
3. The succession and structure east of the Glaslyn river, North Wales;Beavon;Q. J. geol. Soc. Lond.,1963
4. Nomenclature and diagnostic characters of ignimbrites with reference to Snowdonia;Beavon;Lpool Manchr geol. J.,1961
5. Brenchley , P. J. 1966