REVTeX has built-in features for labeling and cross-referencing of section headings, equations, tables, and figures. This section contains a simplified explanation of cross-referencing features. The format for using these features with section headings, equations, tables, and figures is discussed in the appropriate section.
Cross-referencing depends upon the use of ``tags,'' which are defined by
the user. The \label{#1} command is used to identify tags for
REVTeX . Tags are strings of characters that serve to label section
headings, equations, tables, and figures, so that you don't need to know
what number REVTeX has assigned to the item in order to talk about it in
text.
You will need to LaTeX the original file more than once to ensure that the tags have been properly linked to appropriate numbers. If you add any tags, you will need to LaTeX more than once in subsequent work sessions: LaTeX will display an error message that ends with ... Rerun to get cross-references right. If you see that message, LaTeX the file again. If the error message appears after two LaTeX ings, please check your labels; you probably have referred to an item in text without tagging the item.
You may not need to know (or care to know) all about what REVTeX is doing for autonumbering; however, you may want to know that when you LaTeX the file for the first time, an auxiliary file with the .aux filename extension will be created that connects numbers with their tags. Subsequent LaTeX ing accesses the auxiliary file to put the proper number in the text.