-1/2 a^{a0}_{c0} b^{c0}_{a1,a2} a+(a1) a+(a2) a-(a0)
+a^{a1}_{c0} b^{c0}_{a0,a2} eta1^{a2}_{a1} a+(a0)
-a^{a1}_{c0} b^{c1}_{a0,a2} eta1^{a2}_{a1} a+(c0) a+(a0) a-(c1)