0. Preface

## Preface

This online Textbook based on half-year course APM441 at Department of Mathematics, University of Toronto but contains many additions.

• $\Uparrow$ Home (Table of contents). It would be a good idea to add "Home" to your bookmarks.
• $\Leftarrow$ Previous.
• $\Rightarrow$ Next.
• $\Downarrow$ and $\downarrow$ To low level material (say Problems or Appendix to Section).
• $\uparrow$ From low to normal-level material.
##### Source

This Textbook is open (which means that anyone can use it without any permission or fees) and open-source (which means that anyone can easily modify it for his or her own needs) and it will remain this way forever. Source (in the form of Markdown) of each page could be downloaded: this page's URL is

http://www.math.toronto.edu/courses/apm346h1/20161/APM-textbook/Chapter0/L0.html

and its source's URL is

http://www.math.toronto.edu/courses/apm346h1/20161/APM-textbook/Chapter0/L0.md

and for all other pages respectively.