Cuc, Vincenţiu, and Mihail Megan. “On \((h,\,k)\)-Stability in Banach Spaces”. Rev. Anal. Numér. Théor. Approx. 26, no. 1 (August 1, 1997): 53–57. Accessed December 4, 2024. https://ictp.acad.ro/jnaat/journal/article/view/1997-vol26-nos1-2-art8.