TY  - BOOK
AU  - Howells,M.F.
AU  - Leveridge,B.E.
AU  - Evans,C.D.R.
ED  - Her Majesty΄s Stationery Office
TI  - Ordovician ash-flow tuffs in eastern Snowdonia
T2  - Institute of Geological Sciences : Natural Environment Research Council. 73/3
SN  - 0118806033
U1  - 551.73142925 
PY  - 1973///.
CY  - London: 
PB  - Her Majesty's Stationery Office, 
KW  - Ash
KW  - Snowdonia (Wales)
N1  - Includes bibliographical references (p. 33)
ER  -