 Theodosios Pavlidis (1982) suggested the use of graph-theoretic algorithms such as the depth-first search method for finding connected components.Vladimir Kovalevsky (1989) extended the Alexandrov–Hopf 2D grid cell topology to three and higher dimensions.He also proposed (2008) a more general axiomatic theory of locally finite topological spaces and abstract cell complexes formerly suggested by Ernst Steinitz (1908).