Let r be a line through the orthocenter H; ra, rb, rc its reflections on the sides; A', B', C' the intersections between r and the sides. Let Ab, Ac be the orthogonal projections of  A' on rb, rc and define analogously Bc, Ba, Ca, Cb. The ninecenters Na, Nb, Nc of the triangles A'AbAc, B'BcBa, C`CaCb are collinear.