Daearyddiaeth : Prosesau /
Hughes, Cledwyn.
Jones, Sian.
Project Defnyddiau ac Adnoddau y Swyddfa Gymreig.
University College of Wales (Aberystwyth, Wales).Resources Centre.
Great Britain.Welsh Office.
[Aberystwyth] : CAA,
1988.
CAA is funded by the Welsh Office.
Weathering.