“…Also, a new branch of nonlinear approximation theory investigating approximation capabilities of neural networks was developed [11,12,21,28,38,45,50,51,52,53,54,55,56,57,58]. In a series of papers [3,5,8,9,10,64,65,66,80,81], a new method of approximate optimization was developed, called in [81] the extended Ritz method.…”