Systems theory to social sciences (see David Easton's seminal development of the "political system" as an analytical construct), the original theorists explored the implications of twentieth century advances in terms of systems. People have studied subjects like complexity, self-organization, connectionism and adaptive systems in the 1940s and 1950s. In fields like cybernetics, researchers such as Norbert Wiener, William Ross Ashby, John von Neumann and Heinz von Foerster, examined complex systems mathematically. John von Neumann discovered cellular automata and self-reproducing systems, again with only pencil and paper. Aleksandr Lyapunov and Jules Henri Poincaré worked on the foundations of chaos theory without any computer
Norbert Wiener present formulation, the theorem of Wiener does not have any obvious association with Tauberian theorems, which deal with infinite series; the translation from results formulated for integrals, or using the language of functional analysis and Banach algebras, is however a relatively routine process. The Paley–Wiener theorem relates growth properties of entire functions on C and Fourier transformation of Schwartz distributions of compact support. The Wiener–Khinchin theorem, (or "Wiener – Khintchine theorem" or "Khinchin – Kolmogorov theorem"), states that the power spectral density of a wide-sense-stationary random process is the Fourier transform of the corresponding autocorrelation function. An abstract Wiener space