Activation of pro-urokinase and plasminogen on human sarcoma cells: a proteolytic system with surface-bound reactants - Stephens, R W; Pöllänen, J; Tapiovaara, H; Leung, K-C; Sim, P-S; Salonen, E-M; RØnne, E; Behrendt, N; DanØ, K; Vaheri, A (J Cell Biol, 1989)