Authors: Janusz Kaczorowski; Larry W Chambers; Lisa Dolovich; J Michael Paterson; Tina Karwalajtys; Tracy Gierman; Barbara Farrell; Beatrice McDonough; Lehana Thabane; Karen Tu; Brandon Zagorski; Ron Goeree; Cheryl A Levitt; William Hogg; Stephanie Laryea; Megan Ann Carter; Dana Cross; Rolf J Sabaldt Journal: BMJ Date: 2011-02-07