Alex nodded, embarrassed.
Alex took the book. The paper smelled of coffee and decades of midnight oil. And there, on page 42, a handwritten note from a previous reader: “This proof is a bridge. Cross it slowly.” norman l. biggs discrete mathematics pdf
A soft click broke the silence. Across the table, an elderly janitor named Mr. Eldridge was emptying a trash bin. He saw the screen and smiled. “Biggs?” he said. “The orange one? The one with the Penrose triangle on the cover?” Alex nodded, embarrassed