-a^{a0}_{c1} b^{c1,a2}_{c0,v0} c^{a1}_{a3} eta1^{a3}_{a2} a+(c0) a+(v0) a-(a1) a-(a0)
+a^{a2}_{c1} b^{c1,a0}_{c0,v0} c^{a1}_{a3} eta1^{a3}_{a2} a+(c0) a+(v0) a-(a1) a-(a0)