Erdõs, PaulHarcos, GergelyPach, János2008-11-142008-11-142008-11-14199910.1016/S0012-365X(98)00328-8https://infoscience.epfl.ch/handle/20.500.14299/31100Erdõs problemsextremal problemssets of distances of $n$ pointsdirected graphPopular distances in 3-spacetext::journal::journal article::research article