Improved graft patency with anticoagulant therapy after aortocoronary bypass surgery: a prospective, randomised study - Gohlke, H; Gohlke-Barwolf, C; Stiirzenhofecker, P; Gomandt, L; Ritter, B; Reichelt, M; Buchwalsky, R; Schmuziger, M; Roskamm, H (Circulation, 1981)