Humphries, Neil (). „CASE STUDY: The Contribution of Active Surface Mines in the Conservation of Lichen Communities in the South Wales Coalfield, United Kingdom”. Journal American Society of Mining and Reclamation. 2 (1): 80–98. doi:10.21000/jasmr13010080. ISSN2328-8744.
Sherwood, P. T. Alternative materials in road construction : a guide to the use of recycled and secondary aggregates. ISBN9780727745682. OCLC893682144.
Humphries, Neil (). „CASE STUDY: The Contribution of Active Surface Mines in the Conservation of Lichen Communities in the South Wales Coalfield, United Kingdom”. Journal American Society of Mining and Reclamation. 2 (1): 80–98. doi:10.21000/jasmr13010080. ISSN2328-8744.