1. A. K. Bakhtin, Some properties of functions of the class S, Ukrain. Mat. Zh. 33 (1981), 154-159 (in Russian)
2. English translation, Ukrainian Math. J. 33 (1981), 122-126.
3. A. K. Bakhtin, Extrema of linear functionals, Akad. Nauk Ukrain. SSR Inst. Mat. Preprint 1986, no. 25 (in Russian).
4. Louis Brickman, Functionals of rational type over the class S, Proc. Amer. Math. Soc. 92 (1984), 372–376.
5. Johnny E. Brown, Linear extremal problems in the class of univalent functions, Doctoral dissertation, University of Michigan, 1979.