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A new proof of the q -Dixon identity

Victor J. W. Guo (2018)

Czechoslovak Mathematical Journal

We give a new and elementary proof of Jackson’s terminating q -analogue of Dixon’s identity by using recurrences and induction.

A New Proof that 4-Connected Planar Graphs are Hamiltonian-Connected

Xiaoyun Lu, Douglas B. West (2016)

Discussiones Mathematicae Graph Theory

We prove a theorem guaranteeing special paths of faces in 2-connected plane graphs. As a corollary, we obtain a new proof of Thomassen’s theorem that every 4-connected planar graph is Hamiltonian-connected.

A new upper bound for the chromatic number of a graph

Ingo Schiermeyer (2007)

Discussiones Mathematicae Graph Theory

Let G be a graph of order n with clique number ω(G), chromatic number χ(G) and independence number α(G). We show that χ(G) ≤ [(n+ω+1-α)/2]. Moreover, χ(G) ≤ [(n+ω-α)/2], if either ω + α = n + 1 and G is not a split graph or α + ω = n - 1 and G contains no induced K ω + 3 - C .

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