1/8 a^{a1}_{a0} b^{c0,c1}_{c2,c3} c^{c2,c3}_{a2,a3} a+(a0) a+(a2) a+(a3) a-(a1) a-(c1) a-(c0)
-1/2 a^{a2}_{a0} b^{c1,c2}_{c0,c4} c^{c3,c4}_{a1,a3} eta1^{a3}_{a2} a+(c0) a+(a0) a+(a1) a-(c3) a-(c2) a-(c1)
-1/4 a^{a2}_{a0} b^{c0,c1}_{c2,c3} c^{c2,c3}_{a1,a3} eta1^{a3}_{a2} a+(a0) a+(a1) a-(c1) a-(c0)