G planar iff contains no subdivision of K_5 or K_{3,3}. Wagner version: no K_5 or K_{3,3} as minor. Euler formula V − E + F = 2.
G planar iff contains no subdivision of K_5 or K_{3,3}. Wagner version: no K_5 or K_{3,3} as minor. Euler formula V − E + F = 2.