Let $n= 2k+1, |X|=|Y|= n$ and $G= (X, Y, E)$ be a $(k+1)$-regular bipartite graph.
$M $ be a perfect matching of
$G$ having the property that every cycle of size 4
$C_4 $ intersects ` $M$ in at most one edge.
$G $ have a factorization ` $ M, M_1, M_2, ...., M_k$ such that:
for all $1\leq i \leq k$ ` $M \cup M_i$ is a Hamiltonian cycle