1/2 a^{a2,a3}_{a0,a1} b^{v0}_{a4} eta1^{a4}_{a3} a+(a0) a+(a1) a-(v0) a-(a2)
+1/2 a^{a2,a3}_{a0,a1} b^{v0}_{a4} lambda2^{a1,a4}_{a2,a3} a+(a0) a-(v0)