Perhaps you should try some spelling variations:
a literatura » la literatura, a literature, a literatur
y literatura » la literatura
tests scale » tests stable, sets scale, tests safe
student e » student _, student 1, student 3
student a » student _

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: tests scale ((student e) OR (student a)) filosofia ((a literatura) OR (y literatura)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tests scale ((student e) OR (student a)) filosofia ((a literatura) or (y literatura))".
• Adding a wildcard symbol may retrieve word variants: tests scale ((student e) OR (student a)) filosofia ((a literatura) or (y literatura))*.