Jun froze. He typed: Who is this?

But Jun was not looking for a book. He was looking for the book. His professor had described it in hushed tones: "Leithold doesn't just teach you how to derive. He teaches you why the derivative exists. It's the difference between a cook and a chef."

> THE OFFICIAL 7TH EDITION HAS A TYPO ON PAGE 672. THE LIMIT DEFINITION OMITS A CRITICAL 'δ' (DELTA). I SAW IT WHEN LEITHOLD SIGNED MY COPY. HE CROSSED IT OUT WITH A RED PEN AND WROTE: "THE PRINTER'S DEVIL. ALWAYS CHECK THE QUANTIFIER ORDER."

The screen went black.