The following description is based on the paper by Outeiral and co-workers. We divide the whole 3D space R 3 into disjoint (non-overlapping) atomic basins or quantum atoms Ωi (containing only i-th atom) in such a way that the so-called zero-flux condition holds (meaning that the electron density ϱ(⃗ r) stays almost constant while crossing the boundary surface ∂Ωi) and if provided only with the DIs for the nearest bonds, then it is impossible to check the normalization. For example, in the figure45 the sum of nearest DIs sums up to 12.33 pairs, whereas from the electron structure we would expect 14 pairs for the N8 molecule.