-1/864 a^{a6}_{a0,a1,a2} b^{}_{c0,c1,c2,c3} c^{}_{a3,a4,a5,a7} eta1^{a7}_{a6} a+(c0) a+(c1) a+(c2) a+(c3) a+(a0) a+(a1) a+(a2) a+(a3) a+(a4) a+(a5)