Holomorphic solutions of an inhomogeneous Cauchy equation. Luigi Paganoni, S. Paganoni Martegalli (1989) Aequationes mathematicae
Homogeneity properties of subadditive functions. Burai, Pál, Száz, Árpád (2005) Annales Mathematicae et Informaticae
Hyers-Ulam stability of functional equations in several variables. Gian Luigi Forti (1995) Aequationes mathematicae