History
Outerplanar graphs were first studied and named by Chartrand & Harary (1967), in connection with the problem of determining the planarity of graphs formed by using a perfect matching to connect two copies of a base graph (for instance, many of the generalized Petersen graphs are formed in this way from two copies of a cycle graph). As they showed, when the base graph is biconnected, a graph constructed in this way is planar if and only if its base graph is outerplanar and the matching forms a dihedral permutation of its outer cycle.
Read more about this topic: Outerplanar Graph
Famous quotes containing the word history:
“The history of all countries shows that the working class exclusively by its own effort is able to develop only trade-union consciousness.”
—Vladimir Ilyich Lenin (1870–1924)
“The best history is but like the art of Rembrandt; it casts a vivid light on certain selected causes, on those which were best and greatest; it leaves all the rest in shadow and unseen.”
—Walter Bagehot (1826–1877)
“In every election in American history both parties have their clichés. The party that has the clichés that ring true wins.”
—Newt Gingrich (b. 1943)