Harper, D. A. T., Hammarlund, E. U., & Rasmussen, C. M. Ø. (mai 2014). „End Ordovician extinctions: A coincidence of causes”. Gondwana Research. 25: 1294–1307. Bibcode:2014GondR..25.1294H. doi:10.1016/j.gr.2012.12.021.Mentenanță CS1: Nume multiple: lista autorilor (link)
Harper, D. A. T., Hammarlund, E. U., & Rasmussen, C. M. Ø. (mai 2014). „End Ordovician extinctions: A coincidence of causes”. Gondwana Research. 25: 1294–1307. Bibcode:2014GondR..25.1294H. doi:10.1016/j.gr.2012.12.021.Mentenanță CS1: Nume multiple: lista autorilor (link)