Wiener series
ORTHOGONAL EXPANSION FOR NONLINEAR FUNCTIONALS CLOSELY RELATED TO THE VOLTERRA SERIES AND HAVING THE SAME RELATION TO IT AS AN ORTHOGONAL HERMITE POLYNOMIAL EXPANSION HAS TO A POWER SERIES
Wiener kernel
In mathematics, the Wiener series, or Wiener G-functional expansion, originates from the 1958 book of Norbert Wiener. It is an orthogonal expansion for nonlinear functionals closely related to the Volterra series and having the same relation to it as an orthogonal Hermite polynomial expansion has to a power series.