Possible site of coal pit at Hett (Hett) - Source of Reference
| No. | Originator(s) | Date | Title | Notes |
|---|---|---|---|---|
| 1 | Ordnance Survey | Ordnance Survey Archaeology Card AKA National Non-Intensive Archaeological Record (England) | NZ23NE8 | |
| 2 | Page, W, Archibald Constable and Company Limited, Vellacott, C H, Dawsons of Pall Mall, University of London Institute of Historical Research, Louis, H, Gee, H | 1907 | The Victoria County History County Durham Volume II | vol.2, p.322 |