Bell, J; J Holden; T H Pettigrew; K W Sedman (March 1979). "The Marl Slate and Basal Permian Breccia at Middridge, Co. Durham". Proceedings of the Yorkshire Geological Society. 42 (3): 439–60. Bibcode:1979PYGS...42..439B. doi:10.1144/pygs.42.3.439.
Evans, S E; M S King (May 1993). "A new specimen of Protorosaurus (Reptilia: Diapsida) from the Marl Slate (late Permian) of Britain". Proceedings of the Yorkshire Geological Society. 49 (3): 229–234. Bibcode:1993PYGS...49..229E. doi:10.1144/pygs.49.3.229.
Bell, J; J Holden; T H Pettigrew; K W Sedman (March 1979). "The Marl Slate and Basal Permian Breccia at Middridge, Co. Durham". Proceedings of the Yorkshire Geological Society. 42 (3): 439–60. Bibcode:1979PYGS...42..439B. doi:10.1144/pygs.42.3.439.
Evans, S E; M S King (May 1993). "A new specimen of Protorosaurus (Reptilia: Diapsida) from the Marl Slate (late Permian) of Britain". Proceedings of the Yorkshire Geological Society. 49 (3): 229–234. Bibcode:1993PYGS...49..229E. doi:10.1144/pygs.49.3.229.