Freeman JM : The punctum plug : evaluation of a new treatment for the dry eye. Trans Sect Ophthalmol Am Acad Ophthalmol Otolaryngol 79 874-879, 1975.
Willis RM, Folberg R, Krachmer JH, Holland EJ : The treatment of aqueous-deficient dry eye with removable punctal plugs. A clinical and impression-cytologic study. Ophthalmology 94 : 514-518, 1987.
Murube J, Murube E : Treatment of dry eye by blocking the lacrimal canaliculi. Sury Ophthalmol 40 : 463-480, 1996.