Apter, A., Pauls, D.L., Bleich, A., Zohar, A.H., Kron, S., Ratzoni, G., et al. (1993). An epidemiologic study of Gilles de la Tourette’s syndrome in Israel. Archives of General Psychiatry, 50, 734-738.

Leckman, J.F., Riddle, M.A., Hardin. M.T., Ort, I., Swartz, K.L., Stevenson, J. & Cohen, D.J. (1989). The Yale Global Tic Severity Scale: initial testing of a clinician-rated scale of tic severity. Journal of the American Academy of Child and Adolescent Psychiatry, 28, 566-73.