personal link Postiwyd gan Govanus ar 2 Mehefin 2015 yn English https://www.groundstability.com/public/web/home.jspx
OpenStreetMap
Trafodaeth
Sylwadau gan Govanus ar 2 Mehefin 2015 am 19:28
https://www.gov.uk/coal-mining-records-data-deeds-and-documents#historic-data
Sylwadau gan Govanus ar 2 Mehefin 2015 am 19:29
https://www.gov.uk/government/publications/con29m-coal-and-brine-area-polygon-data
Sylwadau gan Govanus ar 2 Mehefin 2015 am 19:52
https://www.gov.uk/government/publications/ngec-regional-prime-maps