Rationale and design of a clinical trial of a low-molecular- weight heparin in preventing clinically important venous thromboembolism in medical patients: the prospective evaluation of dalteparin efficacy for prevention of venous thromboembolism in immobilized patients trial (the PREVENT study) - Vaitkus, PT; Leizorovicz, A; Goldhaber, SZ (Vasc Med, 2002)