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