1. mfrac bevelled : $\raisebox{1ex}{$\frac{c-a}{b-a}$}\!\left/ \!\raisebox{-1ex}{$\frac{c-d}{b-d}$}\right.\in ℝ$
2. differentialD : ${\int }_a^{b}f\left(x\right)dx$
3. InvisibleComma : $a_{ij}$