On 3-simplicial vertices in planar graphs
Endre Boros, Robert E. Jamison, Renu Laskar, Henry Martyn Mulder (2004)
Discussiones Mathematicae Graph Theory
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A vertex v in a graph G = (V,E) is k-simplicial if the neighborhood N(v) of v can be vertex-covered by k or fewer complete graphs. The main result of the paper states that a planar graph of order at least four has at least four 3-simplicial vertices of degree at most five. This result is a strengthening of the classical corollary of Euler's Formula that a planar graph of order at least four contains at least four vertices of degree at most five.