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