Skaug M., Dons C. E., Lauritzen Ørnulf, and Worsley D. “Lower Permian Palaeoaplysinid Bioherms and Associated Sediments from Central Spitsbergen”. Polar Research, vol. 1982, no. 2, Jan. 1982, pp. 57-76, doi:10.3402/polar.v1982i2.7004.