Contrast venography, the gold standard for the diagnosis of deep vein thrombosis: improvement in observer agreement - Lensing, AWA; Biiller, HR; Prandoni, P; Batchelor, D; Molenaar, AHM; Cogo, A; Vigo, M; Huisman, PM; ten Cate, JW (Thromb Haemostas, 1992)