Frey, W. H.; DeSota-Johnson, D.; Hoffman, C.; McCall, J. T. (October 1981). "Effect of stimulus on the chemical composition of human tears". American Journal of Ophthalmology. 92 (4): 559–567. doi:10.1016/0002-9394(81)90651-6. ISSN0002-9394. PMID7294117.
Frey, W. H.; DeSota-Johnson, D.; Hoffman, C.; McCall, J. T. (October 1981). "Effect of stimulus on the chemical composition of human tears". American Journal of Ophthalmology. 92 (4): 559–567. doi:10.1016/0002-9394(81)90651-6. ISSN0002-9394. PMID7294117.
Frey, W. H.; DeSota-Johnson, D.; Hoffman, C.; McCall, J. T. (October 1981). "Effect of stimulus on the chemical composition of human tears". American Journal of Ophthalmology. 92 (4): 559–567. doi:10.1016/0002-9394(81)90651-6. ISSN0002-9394. PMID7294117.