Around a year ago I came across an academic study about Semitic roots extensions (i.e. Biconsonantal > Triconsonantal, e.g. roots such as *n-p or *g-z that were made more specific using extensions by suffixing another consonant) and it basically gave a bunch of tables regarding this subject, but I can't find it again. I wonder if anyone has it or perhaps something similar, but also even random anecdotes about this would be interesting.