Shortly into our study it became clear that the current IUPAC recommendation for Rule 1b is not sufficient. The problem is that although Rule 1b was designed to solve a problem with ring-closure duplicate nodes, the rule as stated also applies to multiple-bond duplicate nodes. As such, we again have in Rule 1b the same issue involving multiple Kekulé structures as for Rule 1a. The problem involves cases such as shown in Figure , where the application of Rule 1b as currently recommended can lead to the inappropriate introduction of stereodescriptors. The issue is just one specific case of more general problem of absent procedures to assign root distances for duplicates resulted from averaging of atomic numbers. Assigning distance to root using the current Rule 1b gives the same problem as found for Rule 1a if an averaging criterion is not applied.