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