Notes on the norm of pre-Schwarzian derivatives of certain analytic functions

In this paper, we obtain sharp bounds for the norm of pre–Schwarzian derivatives of certain analytic functions. Initially this problem was handled by H. Rahmatan, Sh. Najafzadeh and A. Ebadian [Stud Univ Babe\c{s}–Bolyai Math {\bf61}(2): 155–162, 2016]. We pointed out that the proofs by Rahmatan et al. are incorrect and present correct proofs.