Non-cyclic transformations and uniform convergence of Picard sequences Bellen, A.; Volčič, A. — 1972 General Topology and its Relations to Modern Analysis and Algebra
Monotone Methods for Periodic solutions of Second Order Scalar Functional Differential Equations. A. Bellen — 1983 Numerische Mathematik
Stability Analysis of One-Step Methods for Neutral Delay-Differential Equations. Z. Jackiewicz; A. Bellen; M. Zennaro Numerische Mathematik