I have a thesis template with external chapters, preamble, etc. When I compile the main file I get the error `si.sty file not found`. I really don't understand where it is? What shall I do? If I am not wrong I understand that `si.sty` is a package file I might not have. If so, where can I get it and where to put it? I am beginner of LaTex. I use Windows XP and Tex Maker.