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