Day-to-day variability in nap duration predicts medical morbidity in older adults
Health Psychology (2012) - Comment
pubmed: 22369491  doi: 10.1037/a0027374  issn: 1930-7810  issn: 0278-6133 

Natalie D. Dautovich, Daniel B. Kay, Michael L. Perlis, Joseph M. Dzierzewski, Meredeth A. Rowe, Christina S. McCrae