对于给定的图G，经过图中每条边恰好2 次的回路称为图G 的双Euler 回路.-for the given graph G, the map after each side exactly two times the loop known as the G-Euler circuit.

Euler公式来源及其应用，和图论的结合，pdf格式，-Euler formula for the sources and applications, and the combination of graph theory, pdf format,