(en) AG Harvey et S. Payne, « The management of unwanted pre-sleep thoughts in insomnia: distraction with imagery versus general distraction », Department of Experimental Psychology, University of Oxford, (lire en ligne)
Yan Tan Tethera. Cette tradition serait, dans le Yorkshire Dales et en Cumbrie, conservée jusqu’à nos jours. Yorkshire Walks - Counting Sheep, 2012, www.yorkshirewalks.org/diary06/count.html