Perhaps you should try some spelling variations:
"resourcessssssssssssssssssssssssssssss selection functions" » "resourcessssssssssssssssssssssssssssss detection functions" (Expand Search), "resourcesssssssssssssssssssssssssssssss selection functions" (Expand Search)
"source selection function" » "source detection function" (Expand Search), "sources selection function" (Expand Search)

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"resourcessssssssssssssssssssssssssssss selection functions\") OR (\"source selection function\"))~".
• Removing quotes may allow a broader search: (( resourcessssssssssssssssssssssssssssss selection functions ) OR ( source selection function ))~.
• Adding a wildcard symbol may retrieve word variants: (("resourcessssssssssssssssssssssssssssss selection functions") OR ("source selection function"))*.