Sure - in any calculus book, or you can find it on the web. You want to read the section on differentials. Then read about Riemann sums, the limit definition of the definite integral, and the fundamental theorem of calculus.

If you already have a decent understanding of calculus, you can probably get through this stuff in a few hours.

If you want a deeper understanding, then read the same sections in an advanced calculus or real analysis book.