1/4 a^{a0,a1}_{c0,c1} b^{v0}_{c2} c^{c2}_{v0} a+(c0) a+(c1) a-(a1) a-(a0)
-1/2 a^{a0,a1}_{c0,c2} b^{v0}_{c1} c^{c2}_{v0} a+(c0) a+(c1) a-(a1) a-(a0)