Probably the same "research" that the avherald quotes.
For those who have a genuine interest in understanding fume events from a scientific perspective,
this speech by Richard Feynmann is well worth keeping in mind when reading much of the academic literature.
There's huge amounts of, as Trump would put it, "fake science" surrounding fume events. To have any hope of convincing aircraft manufacturers and operators that something needs to be done this fake science needs to be put back in its box and real science take the lead. I'm sure that Dream Buster won't like me saying this, but that's life. Profit-making companies aren't going to be convinced by a bunch of papers that have a worse level of scientific understanding than a 1st year undergraduate, we'll have to do far, far, better than that.