Natural Spline Functions, Their Associated Eigenvalue Problem. Florencio Utreras — 1983 Numerische Mathematik
Smoothing Noisy Data Under Monotonicity Constraints Existence, Characterization and Convergence Rates. Florencio I. Utreras — 1985 Numerische Mathematik
Smoothing and interpolation in a convex subset of a Hilbert space : II. The semi-norm case Charles A. Micchelli; Florencio I. Utreras — 1991 ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique