a^{a1}_{c2} b^{v0}_{a0} c^{c1,c2}_{c0,a2} eta1^{a2}_{a1} a+(c0) a+(a0) a-(v0) a-(c1)
-a^{a1}_{c2} b^{v0}_{a2} c^{c1,c2}_{c0,a0} eta1^{a2}_{a1} a+(c0) a+(a0) a-(v0) a-(c1)