1/4 a^{a0,a1}_{c0,c1} b^{}_{} c^{c0,c1}_{a2,v0} a+(a2) a+(v0) a-(a1) a-(a0)
+1/2 a^{a0,a1}_{c0,c1} b^{}_{} c^{c0,c1}_{a2,v0} eta1^{a2}_{a1} a+(v0) a-(a0)
+a^{a0,a1}_{c0,c2} b^{}_{} c^{c1,c2}_{a2,v0} eta1^{a2}_{a1} a+(c0) a+(v0) a-(a0) a-(c1)