-a^{a1,v0}_{c0,c3} b^{c1,c3}_{a0,a2} c^{v1}_{c2} eta1^{a2}_{a1} a+(c0) a+(c2) a+(a0) a-(v1) a-(v0) a-(c1)
+1/4 a^{a0,v0}_{c1,c2} b^{c1,c2}_{a1,a2} c^{v1}_{c0} a+(c0) a+(a1) a+(a2) a-(v1) a-(v0) a-(a0)
-1/2 a^{a1,v0}_{c1,c2} b^{c1,c2}_{a0,a2} c^{v1}_{c0} eta1^{a2}_{a1} a+(c0) a+(a0) a-(v1) a-(v0)