ABSTRACT
In this chapter and the next we introduce some concepts and theorems from an area of graph theory known as extremal graph theory. Of the many problems encountered in this area, a common one asks for the minimum size of a graph G of a given order which guarantees that G contains a certain subgraph or possesses a certain property. More generally, an extremal problem asks for the maximum or minimum value of a graph theoretic parameter in a class of graphs with a given property.
