1/4 a^{a0,a1}_{c0,c1} b^{v0}_{a2} c^{a3}_{v0} gamma1^{a2}_{a3} a+(c0) a+(c1) a-(a1) a-(a0)
+1/2 a^{a0,a2}_{c0,c1} b^{v0}_{a3} c^{a1}_{v0} eta1^{a3}_{a2} a+(c0) a+(c1) a-(a1) a-(a0)