Corrigendum

On page 9 of (1), under the section "Issue 6: combining more than two drugs", the following error has been identified in the formula for the Combination Index for the Bliss Independence model:

$$\text{CI}=\frac{E_A+E_B+\dots +E_N-E_A{E}_B-E_A{E}_N-E_B{E}_N-\dots -E_A{E}_B\dots E_N}{E_{AB\dots N}}$$

The correct formula for the CI for the Bliss Independence model in the case of a combination with more than two drugs is:

$$\text{CI}=\frac{{\sum }_{A\le i\le N}{E}_i-{\sum }_{A\le i_1\le i_2\le N}{E}_{i_1}{E}_{i_2}+{\sum }_{A\le i_1\le i_2\le i_3\le N}{E}_{i_1}{E}_{i_2}{E}_{i_3}+\dots +{\left(-1\right)}^{N-1}{E}_A{E}_B\dots E_N}{E_{AB\dots N}}$$

The authors apologize for the error.