1/2 a^{a1}_{v0} b^{c0,c1}_{c2,a0} c^{c2}_{a2} eta1^{a2}_{a1} a+(a0) a+(v0) a-(c1) a-(c0)
-1/2 a^{a1}_{v0} b^{c0,c1}_{c2,a2} c^{c2}_{a0} eta1^{a2}_{a1} a+(a0) a+(v0) a-(c1) a-(c0)