Sharon Yahav , In this review - Galland BC, Taylor BJ, Elder DE, Herbison P. Normal sleep patterns in infants and children: a systematic review of observational studies. Sleep Med Rev. 2012 Jun;16(3):213-22. doi: 10.1016/j.smrv.2011.06.001. Epub 2011 Jul 23. PMID: 21784676 - the topic is discussed.