Webster's Revised Unabridged Dictionary
| APA | Webster's. (2011). Bollen. Retrieved September 24, 2026, from http://smartdefine.org/bollen/definitions/1981401 |
| Chicago | Webster's. 2011. "Bollen" http://smartdefine.org/bollen/definitions/1981401 (accessed September 24, 2026). |
| Harvard | Webster's 2011, Bollen, Smart Define, viewed 24 September, 2026, <http://smartdefine.org/bollen/definitions/1981401>. |
| MLA | Webster's. "Bollen" 27 May 2011. Web. 24 September 2026. <http://smartdefine.org/bollen/definitions/1981401> |