Possible solutions Cycles 4 Following problem 4 Graph labeling 4 Graph labelings 4 Incidence matrices 4 Incidence matrix 4 Kernel 4 Labeling 4 Labelings 4 Multiplicative version 4 Polynomial algorithm 4 Positive integers 4 Toric ideal 4 Toric ideals 4 Derechos infringidos 1 Discriminatory system 1 Infringed rights 1 Posibles soluciones 1 Sistema discriminatorio 1