Hinds, William Alfred (1908). American Communities and Co-operative Colonies p. 22 en Internet Archive. "the followers of Beissel were wont to assemble for prayer and worship at midnight, the services lasting till one o'clock, when a second period of sleep till four was allowed." (en inglés)
Randall, David K. (2012). «2. Light My Fire». Dreamland: Adventures in the Strange Science of Sleep(en inglés). W. W. Norton. pp. 17-18. ISBN978-0-393-08393-4.
Koslofsky, C. M. (2011). «An early modern revolution». Evening's Empire: A History of the Night in Early Modern Europe(en inglés). pp. 1-18. ISBN9780511977695. doi:10.1017/CBO9780511977695.001.
Brown, Walter A., MD (26 de mayo de 2006). «Acknowledging Preindustrial Patterns of Sleep May Revolutionize Approach to Sleep Dysfunction». Psychiatric Times(en inglés). «The discoveries of Ekirch and Wehr raise the possibility that interrupted sleep is 'normal' and, as such, these revelations hold significant implications for both understanding sleep and the treatment of insomnia».
sleep.org
«Napping Around the World». Sleep.org(en inglés). 21 de diciembre de 2017. Consultado el 31 de julio de 2023. «In China: Workers often take a break after lunch and put their heads on their desks for an hour-long nap. It's considered a Constitutional right.»
ted.com
Gamble, Jessa (2010). «Our natural sleep cycle». TEDGlobal 2010, Oxford, England (video) (en inglés) (TED Conferences, LLC). Consultado el 31 de julio de 2023. «In today's world, balancing school, work, kids and more, most of us can only hope for the recommended eight hours of sleep. Examining the science behind our body's internal clock, Jessa Gamble reveals the surprising and substantial program of rest we should be observing.»
