Alexander Yu. Solynin, “Exercises on the Theme of Continuous Symmetrization”, Comput. Methods Funct. Theory, 20:3-4 (2020), 465
Leopold KOCZAN, Pawel ZAPRAWA, “Koebe sets for the class of functions convex in two directions”, Turk J Math, 41 (2017), 282
Alexey Lukashov, Dmitri Prokhorov, “Approximation of sgn $(x)$ ( x ) on Two Symmetric Intervals by Rational Functions with Fixed Poles”, Comput. Methods Funct. Theory, 15:4 (2015), 493
Leopold Koczan, Paweł Zaprawa, “Covering problems for functions n-fold symmetric and convex in the direction of the real axis”, Applied Mathematics and Computation, 219:3 (2012), 947
Dmitri Prokhorov, Jan Szynal, “Directional convexity of level lines for functions convex in a given direction”, Proc. Amer. Math. Soc., 131:5 (2002), 1453
