3Daum KM,Good G,Tijerina L.Symptoms in video display terminal operators and the presence of small refractive errors.J Am Optom Assoc,1988,59 (9):691-697.
4Wiggins NP,Daum KM.Visual discomfort and astigmatic refractive errors in VDT use.J Am Optom Assoc,1991,62(9):680-684.