The examples in Figs. 5b -5d all embody 𝒮 3 ℬ 2 partitioning. where three O-atoms (solid blue shading) are the three sites. For Fig. the example is NaHCO3 featuring an H-atom and Naatom as the two bonders (light-red shading), that are permitted to undergo connectivity permutation. The central C-atom (light blue shading) is a spectator of the site complex, and the three sites (O-atoms) are equivalent (exhibiting D3h site-symmetry). In Fig. the example has the same site complex as Fig. ("carbonate") but with a pair of bonders (two equivalent methylene C-atoms) joined through spectators (the central methylene). Partitioning for the description of tautomerism in glycolic acid is shown in Fig. . Here, the symmetry of the sites is broken with two equivalent O-atoms (the "carboxylate") and one distinct (the "alcohol").