17 F.R.D. 143, 147 (D.N.J.1997) ("[T]he work product privilege is governed, even in di- versity cases, by iform federal law..."); S.D. Warren Co. I. E. Elect. Corp., dc 201 F.R.D. 280, 281 (D.Me.2001) federal courts apply federal law when ad ressing the work product doctrine, even in di- versity cases