Zhang, J.; Stringer, M. D. (2010). "Ophthalmic and facial veins are not valveless". Clinical & Experimental Ophthalmology38 (5): 502–510. doi:10.1111/j.1442-9071.2010.02325.x. PMID20491800.
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ncbi.nlm.nih.gov
Zhang, J.; Stringer, M. D. (2010). "Ophthalmic and facial veins are not valveless". Clinical & Experimental Ophthalmology38 (5): 502–510. doi:10.1111/j.1442-9071.2010.02325.x. PMID20491800.