NEW YORK (AP) – The NFL has demanded The New York Times retract a front-page story that called the league’s concussion research flawed and likened the NFL’s handling of head trauma to the tobacco industry’s response to the dangers of cigarettes.

In a letter from its law firm to the general counsels of the newspaper and obtained by The Associated Press, the league says it was defamed by the Times.

The NFL added the story published last Thursday didn’t present any evidence to support the claim the league concealed concussion data.

The NFL issued a veiled threat of legal action.

Times sports editor Jason Stallman says the paper sees no reason to retract anything.