1/2 a^{v0,v2}_{a0,a1} b^{a2}_{v2} c^{v1}_{a3} eta1^{a3}_{a2} a+(a0) a+(a1) a-(v1) a-(v0)
+a^{v0,v2}_{a0,a2} b^{a3}_{v2} c^{v1}_{a1} gamma1^{a2}_{a3} a+(a0) a+(a1) a-(v1) a-(v0)