1/2 a^{c0,a1}_{c4,a0} b^{c1}_{a2} c^{c4,v0}_{c2,c3} eta1^{a2}_{a1} a+(c2) a+(c3) a+(a0) a-(v0) a-(c1) a-(c0)
-1/2 a^{c0,a1}_{c4,a0} b^{c4}_{a2} c^{c3,v0}_{c1,c2} eta1^{a2}_{a1} a+(c1) a+(c2) a+(a0) a-(v0) a-(c3) a-(c0)