Mats Hummels: Adjusting to life back at Borussia Dortmund was easier than I expected
Mats Hummels blunt about Dortmund's form: 'It's pretty astonishing we are so pathetic' - NBC Sports
Manchester United transfer news: Mats Hummels 'tells team-mates' his Borussia Dortmund exit is on the verge of being sealed | The Independent | The Independent
Manchester United get all-clear to sign Borussia Dortmund's Mats Hummels | Borussia Dortmund | The Guardian
Mats Hummels – The unsung hero of German football – Back Page Football
Mats Hummels on what convinced him to make Borussia Dortmund return
Mats Hummels requests transfer from Dortmund to Bayern - Fear The Wall