Reducibility of Graphs and Digraphs

Reducibility of Graphs is one of the importent subject in the restrection problem in Graph Theory.In fact the deletion of vertices(edges) from the graph with certain property, may not maintain the property of the graph. When the graph maintain its property after deletion vertex(edge) from its vertex(edge) set means that we can study the graph with fewer vertices(edges) which simpilfie our study for this graph.