Prosesau a phatrymau /
Jones, Gareth Elwyn.
Cymdeithas y Fainc Sglodion.
Blaenau Ffestiniog : Cymdeithas y Fainc Sglodion,
1999.
Darlith a draddodwyd i = lecture delivered to : Cymdeithas y Fainc Sglodion, 04-03-1999.
Geology