J Headache Pain 2005 Jun 13;6(3):128-34. Epub 2005 May 13.
GGSM, Department of Neurology and Psychiatry, National Institute of Medical Sciences and Nutrition, Salvador Zubirán, Vasco de Quiroga No. 15, Colonia Sección XVI, Delegación Tlalpan, México, D.F. CP 14000, Mexico.