The authors noted that equations (4) and (11) in our paper (Li et al., Reference Li, He and Zhang2022) were presented as equations (4) and (14) respectively in a previous publication by Kartha (Reference Kartha1953) after our paper had been published online. Kartha also stated that Eq. (4) in his publication was a result given by Hettich (Reference Hettich1935). We derived these equations in different ways without being aware of the presence of these two publications.
We apologize for the oversight and not citing these two publications.