You only need to include a section for acknowledgements if you have acknowledgement data. You must retain acknowledgements from any GFDL-licensed documentation from which you draw information, in an Acknowledgements section. Under the terms of the GFDL, you must also include copyrights in your manual for any GFDL-licensed documentation from which you draw information. However, in the context of the GNOME project, you can contact copyright holders for source documentation and ask if they are willing to waive their copyrights in the manual that you are writing. If authors of source documentation do waive their copyrights for your manual, you must still acknowledge your sources in the Acknowledgements section.