But it was written in response to the ongoing fight between DuPont and billionaire investor Nelson Peltz, who has been trying to force his way on to the chemical giant's board. Earlier in the week, influential proxy advisory firm Institutional Shareholder Services recommended that DuPont shareholders elect Peltz and one of the nominees put forth by Peltz's hedge fund, former GE executive John Myers. On Wednesday, another proxy advisory firm, Glass Lewis, backed Peltz's nomination to DuPont's board, but not Myers or any of Trian's other nominees. Trian has put forth four nominees for DuPont's board, which shareholders are scheduled to vote for on May 13. (Update: Lipton has posted the full memo here .) DuPont continues to fight Peltz.