The \markboth and \markright
commands are used in conjunction with the
page style myheadings for setting either both or just the right
heading. In addition to their use with the myheadings page style, you
can use them to override the normal headings in the headings style,
since LaTeX uses these same commands to generate those heads. You
should note that a left-hand heading is generated by the last
\markboth command before the end of the page, while a right-hand
heading is generated by the first \markboth or \markright
that comes
on the page if there is one, otherwise by the last one before the
page.