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