1. Ulam, S.M.: A collection of mathematical problems. In: Interscience Tracts in Pure and Applied Mathematics, No. 8, Interscience, New York (1960)
2. Obłoza M.: Hyers stability of the linear differential equation. Rocznik Nauk.-Dydakt. Prace Mat., 13 (1993)
3. Alsina C., Ger R.: On some inequalities and stability results related to the exponential function. J. Inequal. Appl. 2, 373–380 (1998)
4. Jung S.M.: Hyers-Ulam stability of linear differential equations of first order. Appl. Math. Lett. 17, 1135–1140 (2004)
5. Miura T., Miyajima S., Takahasi S.E.: A characterization of Hyers–Ulam stability of first order linear differential operators. J. Math. Anal. Appl. 286, 136–146 (2003)