Guys like Alfredo Martinez and Fernando Polo from the Barcelona side. Juan Jimenez from Atletico's side, Carlos Forjanes from Real Madrid side + other various AS, Onda Cero and RAC1 journalists just to name some.
This Theo thing has been covered by everyone there is. That's not to say he's 100% going to Madrid or Barcelona, but there certainly seem to be concrete interest from both.
No clubs release any official statements regarding any transfers or transfer rumors until it's done and announced on the website. Atletico President Cerezo said they have not received any bid yet, but did Robert Hernandez or anyone from Valencia ever acknowledge that there were negotiations going on for Paco Alcacer, just to name an example? Just as Paco, this is covered by everyone.
There is reason to believe that this particular rumor and story, has truth behind it.
As for Bellerin, Verratti, Coutinho, Justin Bieber or LeBron James, we still have to wait and see.....