In mathematics, the Hellinger integral is an integral introduced by Hellinger (1909) that is a special case of the Kolmogorov integral. It is used to define the Hellinger distance in probability theory.
Hobson, E. W. (1958), The theory of functions of a real variable and the theory of Fourier's series. Vol. I, New York: Dover Publications, pp. XV+736, MR 0092828, Zbl 0081.27702