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