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1LlyfrCyhoeddwyd 1911“...Geological Survey of Great Britain...”
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2Llyfrgan Manning, P. I. (Peter Inglett), 1928-“...Geological Survey of Great Britain...”
Cyhoeddwyd 1970
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3Llyfrgan Wilson, H. E. (Harold Edmund), 1921-“...Geological Survey of Great Britain...”
Cyhoeddwyd 1966
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4LlyfrCyhoeddwyd 1910“...Geological Survey of Great Britain...”
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5
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6Llyfrgan Wilson, G. V., (George Victor), b. 1886“...Geological Survey of Great Britain...”
Cyhoeddwyd 1922
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7LlyfrCyhoeddwyd 1912“...Geological Survey of Great Britain...”
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8
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9
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10Llyfrgan Whitaker, W. (William), 1836-1925“...Geological Survey of Great Britain...”
Cyhoeddwyd 1881
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11
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12Cyfresol
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13Cyfresol
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14
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15LlyfrCyhoeddwyd 1927“...Geological Survey of Great Britain...”
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16Llyfrgan Whitaker, W. (William), 1836-1925“...Geological Survey of Great Britain...”
Cyhoeddwyd 1877
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17LlyfrCyhoeddwyd 1957“...Geological Survey of Great Britain...”
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18Llyfrgan Ussher, W. A. E. (William Augustus Edmond), 1849-1920“...Geological Survey of Great Britain...”
Cyhoeddwyd 1933
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19
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20