On the use of the Grunsky-Nehari inequality for estimating the fourth coefficient of bounded univalent functions O. Tammi — 1967 Colloquium Mathematicae
On the maximum of a 4 - 3 a 2 a 3 + μ a 2 and some related functionals for bounded real univalent functions Z. J. Jakubowski; H. Siejka; O. Tammi — 1985 Annales Polonici Mathematici