Grimaldi, David; Engel, Michael S. (2005). Michael S. Engel (ed.). Evolution of the insects. Cambridge Evolution Series (illustrated, reprinted.). Cambridge University Press. p.97. ISBN978-0-521-82149-0.
Horikawa, Daiki D (2012). "Survival of Tardigrades in Extreme Environments: A Model Animal for Astrobiology". In Altenbach, Alexander V.; Bernhard, Joan M.; Seckbach, Joseph (eds.). Anoxia. Cellular Origin: life in extreme habitats and astrobiology. Vol.21. pp.205–17. doi:10.1007/978-94-007-1896-8_12. ISBN978-94-007-1895-1.