Nowhere-zero -flow --- нигде не нулевой -поток, везде ненулевой -поток.
A graph admits a nowhere-zero -flow ( is an integer ) if its edges can be oriented and labeled by numbers from so that for every vertex the sum of the incoming values equals the sum of the outcoming ones. A graph without nowhere-zero -flow is called -snark. Note that if a graph is a -snarks then it is a -snark for any integer . Very famous is the 5-flow conjecture of W.T.Tutte which says that there are no bridgeless 5-snarks.