If $G$ is a bipartite graph with bipartition $(A,B),$ then

${\displaystyle \underset{\text{v}\text{i}\text{n}\text{A}}{\overset{?}{}}}$deg$(v)={\displaystyle \underset{v^{\text{'}}\text{i}\text{n}\text{B}}{\overset{?}{}}}$deg$(v^{\text{'}}).)($