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