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