1. Intelligence, M. Gaming Market Forecast, Revenue, Trends | 2022 - 27 | Industry Growth. 2022.
2. R. Bartle, Hearts, clubs, diamonds, spades: Players who suit MUDs. Journal of MUD research, 1996, 1(1): p. 19.
3. N. Yee, Motivations for play in online games. CyberPsychology & behavior, 2006. 9(6): 772–775.
4. N. Yee, The Anatomy of Gaming Motivations: What We Learned from 250,000 Gamers. 2017; Available from: https://www.gdcvault.com/play/1024048/The-Anatomy-of-Gaming-Motivations.
5. Van Dreunen, J. A business history of video games: Revenue models from 1980 to today. in Game Behind the Video Game: Business, Regulations, and Society in the Gaming Industry Conference, New Brunswick, NJ. 2011.