Fulek, RadoslavPach, Janos2019-06-182019-06-182019-06-182019-04-3010.1016/j.dam.2018.12.025https://infoscience.epfl.ch/handle/20.500.14299/157358WOS:000466061100020A thrackle is a graph drawn in the plane so that every pair of its edges meet exactly once: either at a common end vertex or in a proper crossing. We prove that any thrackle of n vertices has at most 1.3984n edges. Quasi-thrackles are defined similarly, except that every pair of edges that do not share a vertex are allowed to cross an odd number of times. It is also shown that the maximum number of edges of a quasi-thrackle on n vertices is 3/2(n-1), and that this bound is best possible for infinitely many values of n. (C) 2019 Published by Elsevier B.V.Mathematics, AppliedMathematicsthracklegraph embeddingparity embeddingprojective plane2-dimensional surfacedischarging methodtext::journal::journal article::research article