Fiala, Anna, et al. “Effects of Head Extension on Peak Airway Pressure During Mask-Ventilation: A Prospective, Randomized, Clinical Single-Centre Trial”. Annals of Anesthesiology and Critical Care, vol. 2, no. 1, Mar. 2017, pp. 1-6, https://journals.sbmu.ac.ir/index.php/anescc/article/view/33417.