Study protocol for a randomised controlled trial of carvedilol versus variceal band ligation in primary prevention of variceal bleeding in liver cirrhosis (CALIBRE trial) oleh Dhiraj Tripathi, Peter Clive Hayes, Paul Richardson, Ian Rowe, James Ferguson, Peter Devine, Jonathan Mathers, Christopher Poyner, Sue Jowett, Kelly Handley, Margaret Grant, Gemma Slinn, Khaled Ahmed, Peter Brocklehurst