v

Set v of ZG-generators for the submodule '

(-1+x)e_a

(-1+y)e_b

(-y+x²)e_c

(-x+y)e_d

(y+xy²+yxy²)e_a+(-1-x-xyx)e_b+(1-yx)e_c+(x+yx+xyx)e_d

(-1-xy-yxy)e_a+(-1-yx-xyx)e_b+(1+y+xyx)e_c+(-x²+yx)e_d