Assiri, E. Q., and M. L. Mogra. “A Unified Approach for Univalent Functions With Negative Coefficients Using the Hadamard Product”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 49, no. 9, Sept. 1997, pp. 1162–1170, https://umj.imath.kiev.ua/index.php/umj/article/view/5113.