1 “... of the extent of heterogeneity and its sources, and the possibility of adjustment by meta-regression or bias...”

2 “... of the extent of heterogeneity and its sources, and the possibility of adjustment by meta-regression or bias...”

3 “... treatment will be biased: If control group patients switch treatments and benefit from the new treatment...”

4 “... treatment will be biased: If control group patients switch treatments and benefit from the new treatment...”