  Paper [1] derived the probability density function (PDF) of a sum of products
of two correlated complex Gaussian zero-mean random variables (RVs) that has
been applied to calculate the error probabilities of a \emph{M}-ary phase shift
keying (\emph{M}-PSK) system. We show that there exist some typos in the
computation and we provide the detailed derivation leading to the correct
expressions.
