T. Hansen et al. “Concordance for Multiple Sclerosis in Danish Twins: An Update of a Nationwide Study”. Multiple Sclerosis 11, № 5 (2005).
452
U. Leibowitz et al. “Epidemiological Study of Multiple Sclerosis in Israel. II. Multiple Sclerosis and Level of Sanitation”. Journal of Neurology, Neurosurgery, and Psychiatry 29, № 1 (1966).