Mutations in hemophilia Bra occur al the 180 Arg-Val activation site or in the catalytic domain of factor IX - Bertina, A M; van der Lunden, I K; Mannucci, P M; Reinalda-Poot, H H; Cupers, R; Doort, S R; Reitsma, P H (J Biol Chem, 1990)