a^{a1}_{v0} b^{c0,v1}_{c1,a0} c^{c1}_{a2} eta1^{a2}_{a1} a+(a0) a+(v0) a-(v1) a-(c0)
-a^{a1}_{v0} b^{c0,v1}_{c1,a2} c^{c1}_{a0} eta1^{a2}_{a1} a+(a0) a+(v0) a-(v1) a-(c0)