Mats Hummels explains why he ultimately chose to return to Borussia Dortmund - Bavarian Football Works
Mats Hummels - Wikipedia
Opinion: Hummels' BVB return is worth the risk – DW – 06/19/2019
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