1. Douglas A. Symbiotic interactions. First Edition edn. New York: Oxford University press; 1994.
2. Douglas A. The symbiotic habit. First Edition edn. New Jersey: Princeton University Press; 2010.
3. Ahmadjian V, Parecer S. Symbiosis: An Introduction to biological associations. Second Edition edn. New York: Oxford University Press; 2000.
4. Smith SE, Read DJ. Mycorrhizal symbiosis. Third Edition edn. Cambridge: Academic Press, Elsevier; 2008.
5. Vacelet J. Etude en microscopie electronique de l’association entre bacteries et spongiaires du genre Verongia (Dictyoceratida). J Microsc Biol Cell. 1975;23:271–88.