Corrigendum to "Improved analytical model for calculating mesh stiffness and transmission error of helical gears considering trochoidal root profile" [Mechanism and Machine Theory 163 (2021) 1–19/104386]. (December 2021) - Chung, Woo-Jin; Park, Jung-Ho; Yoo, Ho-Gil; Park, Young-Jun; Kim, Su-chul; Sohn, Jonghyeon; Lee, Geun-ho