Factor VII-deficient substrate plasmas depleted of protein C raise the sensitivity of the factor VII bio-assay to activated factor VII: an international study - Miller, GJ; Stirling, Y; Esnouf, MP; Heinrich, J; van de Loo, J; Kienast, J; Wu, KK; Morrissey, JH; Meade, TW; Martin, JC; Imeson, JD; Cooper, JA; Finch, A (Thromb Haemost, 1994)