If you followed a link to this article, chances are some well-intentioned editor of this wiki used the template,


but forgot to say what symbol he was referring to. The syntax of references to LaTeX symbols is


So here's what you should do: go back to the article that links here and then edit that article (but not the Lsym template itself, please) to correct the syntax of the reference to the {{Lsym}} template. Thanks!