 A similar method has been followed by Schnyder to prove enhanced bounds and a characterization of planarity based on the incidence partial order.His work stressed the existence of a particular partition of the edges of a maximal planar graph into three trees known as a Schnyder wood.Tutte's spring theorem states that every 3-connected planar graph can be drawn on a plane without crossings so that its edges are straight line segments and an outside face is a convex polygon (Tutte 1963).