Perhaps you should try some spelling variations:
mental function » mental functions, potential function, placental function
men's function » green's function, mixer's function, cell's function
fields hilbert » fields hilbert's, fields hilbertian, field hilbert's
hilbert team » hilbert type, hilbert raum, hilbert e

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: germany ((men's function) OR (mental function)) fields hilbert team.
• Adding a wildcard symbol may retrieve word variants: germany ((men's function) or (mental function)) fields hilbert team*.