personal link Govanus erabiltzaileak 2 Ekaina 2015 datan argitaratua English hizkuntzan https://www.groundstability.com/public/web/home.jspx
OpenStreetMap
Eztabaida
Govanus erabiltzailearen iruzkina 2 Ekaina 2015 19:28-eann
https://www.gov.uk/coal-mining-records-data-deeds-and-documents#historic-data
Govanus erabiltzailearen iruzkina 2 Ekaina 2015 19:29-eann
https://www.gov.uk/government/publications/con29m-coal-and-brine-area-polygon-data
Govanus erabiltzailearen iruzkina 2 Ekaina 2015 19:52-eann
https://www.gov.uk/government/publications/ngec-regional-prime-maps