Propolypeptide of von Willebrand factor circulates in blood and is identical to von Willebrand antigen II - Fay, P J; Kawai, Y; Wagner, D D; Ginsburg, D; Bonthron, D; Ohlsson-Wilhelm, B M; Chavin, S I; Abraham, G N; Handin, R I; Orkin, S H; Montgomery, R R; Marder, V J (Science, 1986)