On improper interval edge colourings
Peter Hudák, František Kardoš, Tomáš Madaras, Michaela Vrbjarová (2016)
Czechoslovak Mathematical Journal
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We study improper interval edge colourings, defined by the requirement that the edge colours around each vertex form an integer interval. For the corresponding chromatic invariant (being the maximum number of colours in such a colouring), we present upper and lower bounds and discuss their qualities; also, we determine its values and estimates for graphs of various families, like wheels, prisms or complete graphs. The study of this parameter was inspired by the interval colouring, introduced...