Stem freemium$ (all stems)

2 papers:

CHI-2015-DergousoffM #crowdsourcing #gamification #mobile

Mobile Gamification for Crowdsourcing Data Collection: Leveraging the Freemium Model (KKD, RLM), pp. 1065–1074.

MSR-2011-Whitehead #data mining #game studies #mining #what

Fantasy, farms, and freemium: what game data mining teaches us about retention, conversion, and virality (keynote abstract) (JW), p. 1.