Key 2007-07-04 20:28:13 2007-07-05 09:33:32 Definition % this is the default PlanetMath preamble. as your knowledge % of TeX increases, you will probably want to edit this, but % it should be fine as is for beginners. % almost certainly you want these \usepackage{amssymb} \usepackage{amsmath} \usepackage{amsfonts} % used for TeXing text within eps files %\usepackage{psfrag} % need this for including graphics (\includegraphics) %\usepackage{graphicx} % for neatly defining theorems and propositions %\usepackage{amsthm} % making logically defined graphics %\usepackage{xypic} % there are many more packages, add them here as you need them % define commands here If one has some data that needs to be sorted or indexed, the \emph{key} is the part of the data that is used to make comparisons (if sorting) or to enter into the \PMlinkescapetext{index}. For example, if one has a list of people the \PMlinkescapetext{field} in the data might be names and addresses. One might sort by last name as a key or by street address as another key.