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