Three-dimensional star formation scaling relations involving star formation rate (SFR), stellar mass (M_*), and molecular gas mass (M_mol). Different colours indicate galaxies at given quenching stages. Additionally, for each group, the confidence ellipsoids and the direction of maximal variation in the space (full lines) are calculated with PCA. Circles show CO-detected galaxies, while diamonds indicate CO non-detected galaxies (with S/N<3). Only SF galaxies form a well-defined linear distribution in the three-dimensional space.