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

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("function spaces using tools") or ((("function systems a tool") OR ("pension systems a tool"))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("function spaces using tools") OR ((("function systems a tool") OR ("pension systems a tool")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"function spaces using tools\") or (((\"function systems a tool\") OR (\"pension systems a tool\"))))".
• Removing quotes may allow a broader search: (( function spaces using tools ) or ((( function systems a tool ) OR ( pension systems a tool )))).
• Adding a wildcard symbol may retrieve word variants: (("function spaces using tools") or ((("function systems a tool") OR ("pension systems a tool"))))*.