1. Allen P. M. (1982) in Igneous Rocks of the British Isles, Lower Palaeozoic volcanism in Wales, the Welsh Borderland, Avon, and Somerset, ed Sutherland D. S. (John Wiley & Sons, London), pp 65–91.
2. Allen, P. M. & Jackson, A. A. 1985. Geology of the country around Harlech. Memoir of the British Geological Survey. Sheet 135 with part of 149.
3. Allen, P. M., Cooper, D. C. et al. 1985. Exploration for porphyry-style copper mineralization near Llandeloy, southwest Dyfed. Mineral Reconnaissance Programme Report of the British Geological Survey. No. 78.
4. THE STRATIGRAPHY OF THE MAWDDACH GROUP IN THE CAMBRIAN SUCCESSION OF NORTH WALES
5. The Cae Coch volcanogenic massive sulphide deposit, Trefriw, North Wales