Hyers-Ulam stability of the linear recurrence with constant coefficients. Popa, Dorian — 2005 Advances in Difference Equations [electronic only]
Inequalities involving the inner product. Popa, Dorian; Raşa, Ioan — 2007 JIPAM. Journal of Inequalities in Pure & Applied Mathematics [electronic only]
On single-valuedness of set-valued maps satisfying linear inclusions. Nikodem, Kazimierz; Popa, Dorian — 2008 Banach Journal of Mathematical Analysis [electronic only]