Preface: Special issue on approximation by linear and nonlinear operators with applications. Part I
Danilo Costarelli

Iyengar-Hilfer fractional inequalities
George A. Anastassiou

Convex combination of data matrices: PCA perturbation bounds for multi-objective optimal design of mechanical metafilters
Giorgio Gnecco and Andrea Bacigalupo

On multidimensional Urysohn type generalized sampling operators
Harun Karsli

Sampling in $\Lambda$-shift-invariant subspaces of Hilbert-Schmidt operators on L2(Rd)
Antonio G. García

A note on convergence results for varying interval valued multisubmeasures
Anca Croitoru, Alina Gavrilu Ţ, Alina Iosif and Anna Rita Sambucini

A numerical comparative study of generalized Bernstein-Kantorovich operators
Uur Kadak and Faruk Özger