The predictive ability of bleeding risk stratification models in very old patients on vitamin K antagonist treatment for venous thromboembolism: results of the prospective collaborative EPICA study - Poli, D; Antonucci, E; Testa, S; Cosmi, B; Palareti, G; Ageno, W; FCSA Italian Federation of Anticoagulation Clinics (J Thromb Haemost, 2013)