Mats Hummels to rejoin Borussia Dortmund from Bayern for £34m | Bayern Munich | The Guardian
The future of Borussia Dortmund captain Mats Hummels remains a mystery | Sports | German football and major international sports news | DW | 21.04.2016
Official: Borussia Dortmund sign Mats Hummels from Bayern Munich - Fear The Wall
Borussia Dortmund to Use Mats Hummels as Make-Shift Forward if World Cup Winner Re-Joins Club - Sports Illustrated
Mats Hummels - Player profile 21/22 | Transfermarkt