Existence of regular sets in circulant quartic graphs: a complete characterization

A. Abdollahi, J. Bagherian, F. Jafari +3

Let $\Gamma =(V,E)$ be a graph and let $a,b$ be nonnegative integers. A nonempty proper subset $C\subset V$ is an \emph{$(a,b)$-regular set} if each vertex of $C$ has exactly $a$ neighbo…