1/2 a^{v0}_{c1} b^{c0,a2}_{a0,a1} c^{c1}_{v0} a+(a0) a+(a1) a-(a2) a-(c0)
-1/2 a^{v0}_{c1} b^{c1,a2}_{a0,a1} c^{c0}_{v0} a+(a0) a+(a1) a-(a2) a-(c0)