Flow-equivalent graphs

Flow-equivalent graphs --- потоко-эквивалентные графы.

Let [math]\displaystyle{ F(G,\lambda) }[/math] be a polynomial in [math]\displaystyle{ \lambda }[/math] which gives the number of nowhere-zero [math]\displaystyle{ \lambda }[/math]-flows in [math]\displaystyle{ G }[/math] independent of the chosen orientation. Two graphs [math]\displaystyle{ R }[/math] and [math]\displaystyle{ S }[/math] are said to be flow-equivalent if [math]\displaystyle{ F(R,\lambda) = F(S,\lambda) }[/math].