La résolution numérique des problèmes différentiels aux conditions initiales par des méthodes de collocation
Local interpolation by a quadratic Lagrange finite element in 1D
We analyse the error of interpolation of functions from the space in the nodes of a regular quadratic Lagrange finite element in 1D by interpolants from the local function space of this finite element. We show that the order of the error depends on the way in which the mutual positions of nodes change as the length of interval approaches zero.
Lower Norm Estimates for Approximate Solutions of Differential Equations with Non-Smooth Coefficients.