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2. The homomorphism equation on semilattices

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3. Optimal bounds for the tangent and hyperbolic sine means

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4. Geometry on the lines of polar spine spaces

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5. Geometric properties of discontinuous fixed point set of (\(\varvec{\epsilon -\delta }\)) contractions and applications to neural networks

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6. Some monotonicity properties in F-normed Musielak–Orlicz spaces

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7. On a certain adaptive method of approximate integration and its stopping criterion

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8. On the Ulam–Hyers stability of the complex functional equation \(\varvec{F(z)+F(2z)+\cdots +F(nz)=0}\)

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9. A generalization of d’Alembert’s other functional equation on semigroups

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10. Sections in functional equations

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11. Packing colorings of subcubic outerplanar graphs

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12. Angular measures and Birkhoff orthogonality in Minkowski planes

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13. Approximate n-idempotents and generalized Aluthge transform

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14. Ulam-stability of a generalized linear functional equation, a fixed point approach

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