As shown in Stats and according to the Datatracker tool and/or the RFC index XML description, around one third of valid RFCs (excluding unclassified early RFCs) are not officially produced by an IETF working group, nor by the IAB and IRTF streams, nor by the IESG. The virtual set concept, in the context of this site, enables the grouping of RFCs (otherwise "isolated") in order to associate them (via "see also" links) to official IETF working groups. As a result, it is easier to identify the RFCs related to a given topic. Each "non-WG" RFC is assigned to a single virtual set (prefixed with '~') with the "~zz" virtual set gathering those "non-WG" RFCs not assigned to a pertinent virtual set yet. Unlike official IETF Working groups, this work is not stable and can be permanently refined.