1/2 a^{a1,v0}_{c0,a0} b^{c1,c2}_{a2,v0} c^{}_{} eta1^{a2}_{a1} a+(c0) a+(a0) a-(c2) a-(c1)
+a^{a1,v0}_{c1,a0} b^{c0,c1}_{a2,v0} c^{}_{} a+(a0) a+(a2) a-(a1) a-(c0)
-a^{a1,v0}_{c1,a0} b^{c0,c1}_{a2,v0} c^{}_{} eta1^{a2}_{a1} a+(a0) a-(c0)
+a^{a1,v0}_{c1,a0} b^{c0,c1}_{a2,v1} c^{}_{} eta1^{a2}_{a1} a+(a0) a+(v1) a-(v0) a-(c0)