Donald J. Galagan, John W. Knutson, The Effect of Topically Applied Fluorides on Dental Caries Experience: V. Report of Findings with Two, Four and Six Applications of Sodium Fluoride and of Lead Fluoride, Public Health Reports (1896-1970), Vol. 62, No. 41 (Oct. 10, 1947), pp. 1477-1483
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