[wiki]In graph theory, a regular graph is a graph where each vertex has the same number of neighbors; i.e. every vertex has the same degree or valency. A regular directed graph must also satisfy the stronger condition that the indegree and outdegree of each vertex are equal to each other.
I support this : regular graph should be simple graph .
But another link is doubtful for me.
Please clarify this :
Is it necessary for a regular graph to be simple graph also ?