Ridgway says working on the book challenged him intellectually and emotionally.

VOA: standard.2009.10.21

The president invited about and challenged them to help him find ways to put millions of Americans back to work.

VOA: standard.2009.12.04

"I called the journalist who first wrote this and challenged him to show proof, " he says.

FORBES: Rice War

The moderator challenged him on the statement, giving Ford an opportunity to change his words.

NPR: Ford Remembered in His Own Words

They had been arguing and his sister was distressed and McGarry challenged him about this.

BBC: Cairin McGarry jailed for West Lothian flat knife attack