This paper considers delta estimators of the Radon-Nikodym derivative of a probability function with respect to a σ-finite measure. We provide sufficient conditions for universal consistency, which are checked for some wide classes of nonparametric estimators.This paper considers delta estimators of the Radon-Nikodym derivative of a probability function with respect to a σ-finite measure. We provide sufficient conditions for universal consistency, which are checked for some wide classes of nonparametric estimators.[+][-]