-1/4 a^{a3}_{a0} b^{c0,v0}_{a1,a2} c^{c1,c2}_{a4,v0} eta1^{a4}_{a3} a+(a0) a+(a1) a+(a2) a-(c2) a-(c1) a-(c0)
+1/2 a^{a3}_{a0} b^{c0,v0}_{a1,a4} c^{c1,c2}_{a2,v0} eta1^{a4}_{a3} a+(a0) a+(a1) a+(a2) a-(c2) a-(c1) a-(c0)