nited States v. Feldman, 83 F.3d 9, 14 (1st Cir. 1996) (defendant's letters of apology not protected because voluntarily prepared); In re Grand Jury Subpoena Duces Tecutn, 1 F.3d 87, 90 (2d Cir. 1993) (defendant's personal calendar not protected because voluntarily prepared); Barrett v. Acevedo, 169 F.3d 1155, 1168 (