Carl Darling Buck (A Dictionary of Selected Synonyms in the Principal Indo-European Languages) and Julius Pokorny (Indogermanisches Etymologisches Wörterbuch) are just a few of the philologists who have posited this "dead water" hypothesis
Neither Buck nor Pokorny are regarded today as worth citing except for historiographical reasons. Their work is obsolete by many decades.
Could you recommend a book or reading material that reflects recent developments in PIE research? I have a few books but they’re quite old.
It's funny how you cited sources and rather than be given information you were just told that you were very wrong without any attempt to distill knowledge.
For someone in the field, teaching is work, while telling people they are wrong isn't. Unless you are paying good money, you don't have a right to the former instead of the latter. In any event, the GP (note: not the same as the OP) could just look for himself on the shadow libraries, which now have pretty much everything.
I didn’t cite sources. You’re confusing me with someone else.