1/2 a^{a0,a1}_{c1,v0} b^{c1,a2}_{a3,v1} c^{a4}_{c0} gamma1^{a3}_{a4} a+(c0) a+(v0) a+(v1) a-(a2) a-(a1) a-(a0)
-a^{a0,a3}_{c1,v0} b^{c1,a1}_{a4,v1} c^{a2}_{c0} eta1^{a4}_{a3} a+(c0) a+(v0) a+(v1) a-(a2) a-(a1) a-(a0)