Tutte's 5‐flow conjecture for the projective plane
Richard Steinberg · Journal of Graph Theory · 1984
Abstract Heawood proved that every planar graph with no 1‐cycles is vertex 5‐colorable, which is equivalent to the statement that every planar graph with no 1‐bonds has a nowhere‐zero 5‐flow. Tutte has conjectured that every graph with no 1‐bonds has a nowhere‐zero 5‐flow. We show that Tutte's 5‐Flow Conjecture is true for all graphs embeddable in the real projective plane.