Barclay W.J.; Browne M.A.E.; McMillan A.A.; Pickett E.A.; Stone P.; Wilby P.R., eds. (2005). "1: Introduction to the Old Red Sandstone of Great Britain"(PDF). The Old Red Sandstone of Great Britain. Geological Conservation Review Series. Vol. 31. Joint Nature Conservation Committee. ISBN978-1-86107-543-7. Archived from the original(PDF) on 7 March 2012. Retrieved 26 February 2012.
Rance, Hugh (1999). "Hutton's unconformities"(PDF). Historical geology: the present is the key to the past. QCC Press. Archived from the original(PDF) on 2008-12-03. Retrieved 2008-10-20.
Barclay W.J.; Browne M.A.E.; McMillan A.A.; Pickett E.A.; Stone P.; Wilby P.R., eds. (2005). "1: Introduction to the Old Red Sandstone of Great Britain"(PDF). The Old Red Sandstone of Great Britain. Geological Conservation Review Series. Vol. 31. Joint Nature Conservation Committee. ISBN978-1-86107-543-7. Archived from the original(PDF) on 7 March 2012. Retrieved 26 February 2012.
Rance, Hugh (1999). "Hutton's unconformities"(PDF). Historical geology: the present is the key to the past. QCC Press. Archived from the original(PDF) on 2008-12-03. Retrieved 2008-10-20.