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On the Renorming of a Vector Space Endowed with Two Norms and the Simultaneous Best Approximation Problem. N. Hadjisavvas; Nassopoulos B. — 1988 Mathematische Annalen
Über die Existenz gemeinsamer Elemente bester Approximation bezüglich zweier Normen. N. Hadjisavvas; B. Nassopoulos — 1987 Manuscripta mathematica
Hadamard-type inequalities for quasiconvex functions. Hadjisavvas, N. — 2003 JIPAM. Journal of Inequalities in Pure & Applied Mathematics [electronic only]