1/2 a^{c0,a1,a2}_{a0} b^{}_{c1,a3,v0,v1} eta1^{a3}_{a2} a+(c1) a+(a0) a+(v0) a+(v1) a-(a1) a-(c0)
-1/4 a^{c0,a1,a2}_{a0} b^{}_{c1,a3,v0,v1} lambda2^{a0,a3}_{a1,a2} a+(c1) a+(v0) a+(v1) a-(c0)