Perhaps you should try some spelling variations:
"function spaces using tools" » "function systems using tools", "function space using tools", "function gases using tools", "function paper using tools"
"pension systems _ tools" » "poisson systems _ tools", "suspension system _ tools", "function systems _ tools"
"fusion system _ tools" » "diffusion systems _ tools", "function systems _ tools"

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: "((\"function spaces using tools\") OR (((\"pension systems _ tools\") OR (\"fusion system _ tools\"))))~".
• Removing quotes may allow a broader search: (( function spaces using tools ) OR ((( pension systems _ tools ) OR ( fusion system _ tools ))))~.
• Adding a wildcard symbol may retrieve word variants: (("function spaces using tools") OR ((("pension systems _ tools") OR ("fusion system _ tools"))))*.