Ref. , the authors analyzed the intramolecular H-bonds of different configurations of benzo[a]pyrene diol epoxide using the NCI method and discussed the relative stability of the configurations. Additionally, many application examples can be found in review articles by us and others, as well as in the original paper of the NCI method. Our recent review also discusses some technical details of performing NCI analysis, such as the computational level required for electron density, the reasonable choice of grid spacing for calculating RDG and sign(2) grid data, and the proper preparation of geometry.