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