Glossary of "Evolution (4th ed.)" by Futuyma & Kirkpatrick (2017)
- An ecological relationship between species in which one is benefited but the other is little affected.
Glossary of "Environmental Science: Earth as a Living Planet (2nd ed.)" by Botkin & Keller (1998)
- A relationship between two kinds of organisms in which one benefits from the relationship and the other is neither helped nor hurt.
- Botkin, D. B. & Keller, E. A. 1998. Environmental Science: Earth as a Living Planet, 2nd ed. -xxxxii + 649 pp. John Wiley & Sons, Inc., New York.
- Futuyma, D. J. & Kirkpatrick, M. 2017. Evolution, 4th ed. -xviii + 602 pp. Sinauer Associates, Inc., Sunderland.