This group of commands can be used to create your own document class or
package by building on existing classes or packages.
Packages and classes should use this command to load other packages.
Its use is the same as the author command |.
Example:
\RequirePackage{ifthen}[1994/06/01]
This command is for use only in class files, it cannot be used
in packages files. It is used in the same way as |, to
load a class file.
Also, it can be used at most once within a class file.
Example:
\LoadClass{article}[1994/06/01]