Popa, Dorian. “Set-Valued Solutions for an Equation of Jensen Type”. Rev. Anal. Numér. Théor. Approx. 28, no. 1 (February 1, 1999): 73–77. Accessed May 19, 2024. https://ictp.acad.ro/jnaat/journal/article/view/1999-vol28-no1-art6.