No problem Bernard. You can do even far more detailed searches in the library.
When you open resources with button the top bar. You will find a section called "Categories" at the left side of the page. This contains a series of dropdown menus which can bring you to for instance FS2004 scenery.
When you click on the search button in the topbar now, the earlier mentioned dropdown menu, which starts with "everywhere" in the search field, will contain the extra option "this category".
Now it will only search the category selected.
Cheers,
Huub