Contrast venography, the gold standard for the diagnosis of deep vein thrombosis: Improvement in observer agreement - Lensing, A WA; Büller, H R; Prandoni, P; Batchelor, D; Molenaar, A HM; Cogo, A; Vigo, M; Huisman, P M; ten Cate, J W (Thromb Haemost, 1992)