- Veenhoven, R.
- Findings on Happiness and Sleep.
- World Database of Happiness, Collection of Correlational Findings, Finding report S4, Erasmus University Rotterdam, The Netherlands, Printout 2009, http://worlddatabaseofhappiness.eur.nl.
- English (Australia, Canada, UK, USA)
Eligible for inclusion in findings archive
- No, no new data on present happiness.