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