Perhaps you should try some spelling variations:
stumpff function » sumif function, studies function, staff functions
study functional » studies functional, lazy functional, fully functional
study function » studies function, study section, body function

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

• If you are trying to use Boolean operators, they must be ALL CAPS: ((stumpff function) OR (((study function) OR (study functional)))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((stumpff function) or (((study function) OR (study functional))))".
• Adding a wildcard symbol may retrieve word variants: ((stumpff function) or (((study function) OR (study functional))))*.