Perhaps you should try some spelling variations:
del literatura » de literatura, pela literatura, da literatura
series state » services state, series study
studenten di » studenten die, studenten i, studenten vi
di filosofia » la filosofia, e filosofia
series some » services some, series sum, theories some

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: ((series some) OR (series state)) studenten di filosofia del literatura.
• Adding a wildcard symbol may retrieve word variants: ((series some) or (series state)) studenten di filosofia del literatura*.