https://pubmed.ncbi.nlm.nih.gov/6725561/
This is just the first google result, there are countless others. And it is quite common knowledge.
It's a comment in a discussion, not a research contribution. It should be judged (not "peer reviewed" as some research claim, but judged and accepted or not as a comment in a discussion) based on whatever it has merit to the best of the participants knowledge, like any other claim.
Not based on whether it comes with a bibliography. If someone wants, they can go and verify it.