Euler Digraph

EULER DIGRAPHS
In a digraph G a closed directed walk (i.e., a directed walk that starts and ends at the same vertex) which transverses every edge of G exactly once is called a directed Euler line.

A graph containing a directed Euler line is called an Euler digraph.

For example, the graph in Fig. 8.15, is an Euler digraph, in which the walk a b c d e f is an Euler line.