Daróczy, Z., Páles, Z.:
A characterization of nonconvexity and its applications in the theory of quasi-arithmetic means.
In: Inequalities and Applications : Conference on Inequalities and Applications, Noszvaj (Hungary), September 2007. Eds.: Catherine Bandle, László Losonczi, Attila Gilányi, Zsolt Páles and Michael Plum, Birkhauser Verlag, Basel, 251-260, 2009, (International Series of Numerical Mathematics ; 157.)