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