1. AARP. (2000). AARP survey on lifelong learning. Harris Interactive Inc. https://www.aarp.org/content/dam/aarp/research/surveys_statistics/life-leisure/lifelong-learning-aarp.doi.10.26419%252Fres.00215.001.pdf.
2. Bang, H., Won, D., & Kim, Y. (2009). Motivations, commitment, and intentions to continue volunteering for sporting events. Event Management, 13(2), 69–81. https://doi.org/10.3727/152599509789686317.
3. Black, B., & Jirovic, R. L. (1999). Age differences in volunteer participation. The Journal of Volunteer Administration, 7, 38–47.
4. Bradly, B. D. (2000). A reason to rise each morning: The meaning of volunteering in the lives of older adults. Generations: Journal of the American Society on Aging, 23(4), 45–50.
5. Bryen, L., & Madden, K. M. (2006). Bounce-back of episodic volunteers: What makes episodic volunteers return? (Working Paper No. CPNS 32). Centre of Philanthropy and Nonprofit Studies. http://www.serviceandinclusion.org/presentations/presentations/NCVS%202013/Episodic%20Service/CPNS_Working_Paper_No_32.pdf.