-a^{a0}_{c2} b^{c0,v1}_{a1,v0} c^{c2}_{c1} eta1^{a1}_{a0} a+(c1) a+(v0) a-(v1) a-(c0)
+a^{a0}_{c2} b^{c2,v1}_{a1,v0} c^{c1}_{c0} eta1^{a1}_{a0} a+(c0) a+(v0) a-(v1) a-(c1)