Fed. R.Civ.P. 26(b)(3) provided: Trial Preparation: Materials. Subject to the provisions of subdivision (b)(4) of this rule, a party may obtain discovery of documents and tangible things otherwise discoverable under subdivision (b)(1) of this rule and prepared in anticipation of litigation or for trial by or for another party or by or for that other party's representative (including his attorney, consultant, surety, indemnitor, insurer, or agent) only upon a showing that the party seeking discovery has substantial need of the materials in the preparation of his case and that he is unable without undue hardship to obtain the substantial equivalent of the materials by other means. In ordering discovery of such materials when the required showing has been made, the court shall protect against disclosure of the mental impressions, conclusions, opinions, or legal theories of an attorney or other representative or a party concerning the litigation. In Bogosian v. Gulf Oil Corp., 738 F.2d 587 (3d Cir.1984) the Third Circuit considered the applicability of the attorney work product doctrine to materials an attorney provided to an expert in an antitrust class action. The materials included 115 documents alleged to contain both "fact" and "opinion" attorney work product. the Court of Appeals reversed a trial court's direction that all work product materials shown to the testifying expert should be disclosed. In doing so, the court stressed the interaction of then existing Fed. R.Civ.P. 26(b)(3) & (4) on attorney work product issues. Fed. R.Civ.P. 26(b)(3) does permit discovery of testifying experts "subject to the provisions of. . . . Fed. R.Civ.P. 26(b)(4). . . ." Fed. R.Civ.P. 26(b)(4) at that time permitted the discovery through interrogatories of facts known and opinions held by testifying experts. According to the Third Circuit, when these two sub-parts of Fed. R.Civ.P. 26 are read together, the provision in Fed. R.Civ.P. 26(b)(3) which requires a court to ". . . .protect against disclosure of the mental impressions, conclusions, opinions or legal theories of . . . .the attorney", trumps the disclosure requirements of Fed. R.Civ.P. 26(b)(4). Id. at 595.