http://xyst.i2p/inciter_riecg.html
References H. Luo, J. Baum, and R. Lohner, Edge-based finite element scheme for the Euler equations , AIAA Journal, 32(6), 1183-1190, 1994. R. Löhner, Edges, stars, superedges and chains , Computer Methods in Applied Mechanics and Engineering, 111, 3-4, 255-263, 1994.