In this paper, \(E_2\)-cordiality of a graph \(G\) is considered. Suppose \(G\) contains no isolated vertex, it is shown that \(G\) is \(E_2\)-cordial if and only if \(G\) is not of order \(4n + 2\).
Citation
Qing Liu, Zhishan Liu. A Necessary and Sufficient Condition for a Graph to be \(E_2\)-Cordial[J], Ars Combinatoria, Volume 123. 159-167. .