In Wizard and Glass, Stephen King makes some pretty clear connections to his other works. It becomes crystal clear that the Dark Tower is a door that opens directly into King's other books. But direct references to Stephen King and his work began to appear in other places much earlier in the series.
Twice Eddie Dan makes mention of The Shining. These are cultural references. Interestingly, both times he is referencing the Kubrick film. Here are two quotes about The Shining from The Drawing Of The Three:
1. While looking through the doorway into Oedtta's world:
Now the view through the doorway made one of those turns the gunslinger found so dizzying— but Eddie found this same abrupt swoop oddly comforting. Roland had never seen a movie. Eddie had seen thousands, and what he was looking at was like one of those moving point-of-view shots they did in ones like Halloween and The Shining. He even knew what they called the gadget they did it with. Steadicam. That was it. (P.198)2. Again, looking through Odetta's eyes:
He was staring into the doorway, hypnotized, as an aisle of Macy’s rushed forward— he was reminded again of The Shining, where you saw what the little boy was seeing as he rode his trike through the hallways of that haunted hotel. He remembered the little boy had seen this creepy pair of dead twins in one of those hallways. (P.223)
Someone has pointed out that Room 217 can equal 19 (2 + 17). Deep. And -- "Another instance of 19 occurs during the climax of the novel, when Jack is attempting to kill his wife, and the book mentions that there are 19 stairs from the lobby to the first floor of the hotel."