Joe,
I found that page by starting in the Documentation Center and typed "esc" figuring that most of the special characters use esc. The first link that came up was "Special Characters: Mathematical and Other Notation". This was an overview of many characters but it referenced the complete tutorial at the bottom.
Often I find the best information by starting with a related topic (as close as I can get) and scrolling to the bottom of the documentation page and clicking on the related tutorials, guides, and links -- the pages are usually well linked. I also think the related commands are usually well done.
Regards,
Neil