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
Advances in Complex Systems Advances in Complex Systems Advances in Complex Systems (ACS) is a peer-reviewed journal published quarterly by World Scientific providing a multidisciplinary perspective to the study of complex systems. The journal was founded in 1997 and aims to "promote cross-fertilization of ideas among all the scientific disciplines having to deal with their own complex systems". Papers in ACS are divided into five sections, each managed by a separate editor: Physics and Mathematics; Computer Sciences; Biological Systems; Social and Economic Systems; and Traffic and Environmental Systems. The journal is indexed in "Mathematical Reviews, CSA Human Population and the Environment Abstracts, CSA Risk