1. Volunteer. Dictionary.cambridge.org. https://dictionary.cambridge.org/dictionary/english/volunteer?q=volunteering
2. Geiser, C., Okun, M.A. and Grano, C. (2014) Who Is Motivated to Volunteer? A Latent Profile Analysis Linking Volunteer Motivation to the Frequency of Volunteering. Psychological Test and Assessment Modeling, 56, 3-24.https://www.researchgate.net/publication/268688031_Who_is_motivated_to_volunteer_A_latent_profile_analysis_linking_volunteer_motivation_to_frequency_of_volunteering
3. Yeung, J.W.K., Zhang, Z. and Kim, T.Y. (2018) Volunteering and Health Benefits in General Adults: Cumulative Effects and Forms. BMC Public Health, 18, Article No. 8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5504679/
4. Volunteering Statistics and Trends for Nonprofits. Nonprofits Source. https://nonprofitssource.com/online-giving-statistics/volunteering-statistics/
5. Ministry of Human Resource and Social Development. https://hrsd.gov.sa/en/