  In the present paper we estimate the norm of the pre-Schwarzian derivative of
bi-starlike functions of order $\alpha$ where $\alpha\in[0,1)$. Initially this
problem was handled by Rahmatan et al. in [Bull Iran Math Soc {\bf43}:
1037-1043, 2017]. We pointed out that the proofs and bounds by Rahmatan et al.
are incorrect and present correct proofs and bounds.
