While I do programming, I need to search for references. I want a free (and maybe open-source) software to do that for me. It should also be compatible with Linux. As most softwares and libraries use Doxygen to generate documentations, I want that will support Doxygen too. I've used Devhelp, but this only works with documentations of GNOME softwares and libraries. I have also tried Zeal, but it also has a limited amount of documentation.