Some useful website links:
- Longtown and District Historical Society http://www.lhsarchive.org.uk/
- Ewyas Lacy Study Group. http://www.ewyaslacy.org.uk/
- Longtown Castle. https://en.wikipedia.org/wiki/Longtown_Castle
- Longtown Castle. http://www.english-heritage.org.uk/visit/places/longtown-castle/
- Longtown Castle. http://www.castlewales.com/longtown.html
- Longtown Castle. http://www.britainexpress.com/attractions.htm?attraction=3496
- Longtown Castle. http://www.gatehouse-gazetteer.info/English%20sites/1429.html
- Ponthendre Castle http://www.gatehouse-gazetteer.info/English%20sites/1461.html
- Historic England. https://www.historicengland.org.uk
- Herefordshire Archaeology. http://htt.herefordshire.gov.uk/herefordshire-archaeology/
- Aerial-Cam. http://www.aerial-cam.co.uk/
- Paul Martin Remfry’s castle books and tours http://www.castlewales.com/home.html
- Castle Studies Group http://www.castlestudiesgroup.org.uk/
- Stratascan Ltd https://www.linkedin.com/company/stratascan