Sleep quality vs. quantity

Prevalence and Correlates of Nonrestorative Sleep Complaints
Maurice M. Ohayon

Sleep quality versus sleep quantity: relationships between sleep quality and measures of health, well-being and sleepiness in college students
June J. Pilcher, Douglas R. Ginter and Brigitte Sadowsky

Sleep and sleep disturbances: biological basis and clinical implications
N. Zisapel

Prolonged-release melatonin for the treatment of insomnia: targeting quality of sleep and morning alertness
Alan Wade, Nava Zisapel, Patrick Lemoine