Low molecular weight heparin once daily compared with conventional low-dose heparin twice daily. A prospective double-blind multicentre trial on prevention of postoperative thrombosis - Bergqvist, D; Burmark, U S; Frisell, J; Hallböck, T; Lindblad, B; Risberg, B; Tömgren, S; Wallin, G (Br J Surg, 1986)