A Connecticut Yankee in King Arthur's Court is a novel written by Mark Twain in the 19th century.
The novel is about a man from the 19th century traveling back in time to the 6th century AD. Having written this book, Clemens easily accepted the possibility that Data and others from the Enterprise-D were from the future, when those were trapped in the San Francisco of 1893.
When Clemens talked with a reporter over his suspicions about Data, the reporter didn't believe it to be real and asked if this were a sequel to A Connecticut Yankee in King Arthur's Court. (TNG: "Time's Arrow, Part II")
In the holodeck program Fair Haven, hologram Michael Sullivan received a copy of this novel from Kathryn Janeway. Sullivan had never read this before. (VOY: "Spirit Folk")