“…By Theorem 8.1, though, this kernel is the Lie algebra gr L pAq, which indeed has degree 1 piece equal to Z " xa 3 y, but also has degree 2 piece equal to Z 2 " xra 1 , a 3 s, ra 2 , a 3 sy, and so on. In fact, it follows from [32,25] that gr L n pAq -Lie n´1 pZ 2 q for n ě 2, although of course grpAq " LiepZ 3 q.…”