1. [1] Bittner R., On certain axiomatics for the operational calculus, ‘Bull. Acad. Polon. Sci.’, Cl. III, 1959, 7(1), pp. 1–9.
2. [2] Bittner R., Operational calculus in linear spaces, ‘Studia Math.’, 1961, 20, pp. 1–18.10.4064/sm-20-1-1-18
3. [3] Bittner R., Algebraic and analytic properties of solutions of abstract differential equations, ‘Rozprawy Matematyczne’ [‘Dissertationes Math.’], 42, PWN, Warszawa 1964.
4. [4] Bittner R., Rachunek operatorów w przestrzeniach liniowych, PWN, Warszawa 1974 [Operational Calculus in Linear Spaces — available in Polish].
5. [5] Elaydi S., An Introduction to Difference Equations, Springer Sci. and Business Media, New York 2005.