Who won the Oscar for Best Actor for 'Dallas Buyers Club'?

For which film did Colin Firth win the Oscar for Best Actor? Who won the Oscar for Best Actor for 'The Artist'? For which film did Jean Dujardin win the Oscar for Best Actor? Who won the Oscar for Best Actor for 'Lincoln'? For which film did Matthew McConaughey win the Oscar for Best Actor? Who won the Oscar for Best Actor for 'The Theory of Everything'? For which film did Eddie Redmayne win the Oscar for Best Actor? Who won the Oscar for Best Actor for 'The Revenant'?