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@article{AM2_1991__42_3_137416, author = {L\'aszl\'o Sz\'ekelyhidi}, title = {Mean-value type functional equations.}, journal = {Aequationes mathematicae}, pages = {23--36}, publisher = {mathdoc}, volume = {42}, number = {3}, year = {1991}, zbl = {0741.39013}, url = {http://geodesic.mathdoc.fr/item/AM2_1991__42_3_137416/} }
László Székelyhidi. Mean-value type functional equations.. Aequationes mathematicae, Tome 42 (1991) no. 3, pp. 23-36. http://geodesic.mathdoc.fr/item/AM2_1991__42_3_137416/