I'm trying to get information to appear above and below a math symbol such as \sum or \leftrightarrows. I've found information detailing \mathop and the syntax behind it but when I try to use it, it appears my tex editor doesn't recognize it as a command. Is mathop not in the ams math package?
I'm a relatively new latex user so any help would be appreciated.
The tutorial I'm following is http://truonglatex.wordpress.com/2010/04/13/arrows-and-stack-math-symbols/
My output looks as the attached image. The code is identical to the one on the website.
Thanks any help would be appreciated.