Not nubered sections in the headers?

[Davide Anchisi]

Hi,

I need to get some not numbered section (e.g. Preface) in the headers of
the document (class: article). At the moment I get the previous
section's name ( i.e. Index) in the headers and not the current
not-numbered one (i.e. Preface).
How can I solve that?

Thank you,

    Davide