Maintenance work on the ZORA database servers is scheduled for Thursday 25th July 2019 from 19:00-20:00. During this period ZORA and JDB will not be available. Thank you for your understanding.
Sommer, K; Ruch, Willibald (2009). Cheerfulness. In: Lopez, Shane J. The encyclopedia of positive psychology. Malden, Mass., US: Wiley-Blackwell, 144-148.