Pongsuthirak, P. “Comparison Between Headfirst and Tail-First Direction of Sperm for Intracytoplasmic Sperm Injection”. International Journal of Reproduction, Contraception, Obstetrics and Gynecology, vol. 8, no. 11, Oct. 2019, pp. 4177-81, doi:10.18203/2320-1770.ijrcog20194601.