Many have questioned President Donald Trump’s understanding of the U.S. Constitution, but a new book suggests he might be incapable of reading it.

Washington Post reporters Philip Rucker and Carol Leonnig have a new book about the Trump presidency, “A Very Stable Genius,” based on hundreds of hours of interviews with more than 200 sources, and much of it backed by documentary evidence.

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In one episode from the book, Trump agreed early in his presidency to take part in an HBO documentary featuring judges, lawmakers and all the living presidents reading aloud from the Constitution.

But Trump struggles and stumbles over the words, according to the book, and blames others in the room for his bungling.

“It’s like a foreign language,” he complained, according to the book.