1 research outputs found
On the upper and lower chromatic numbers of BSQSs(16)
A mixed hypergraph is characterized by the fact that it possesses C-edges as well as D-edges. In a colouring of a mixed hypergraph, every C-edge has at least two vertices of the same colour and every D-edge has at least two vertices coloured differently. The upper and lower chromatic numbers , are the maximum and minimum numbers of colours for which there exists a colouring using all the colours