1. Tier und Pflanze in intrazellulärer Symbiose;Buchner,1921
2. Symbiosis as a Source of Evolutionary Innovation;Margulis,1991
3. Evolution by Association;Sapp,1994
4. Generating novelty by symbiosis;Smith;Nature,1989
5. Leaving the cradle;Strohm;Zoology,1995