Perhaps you should try some spelling variations:
letteratura sarda » letteratura storia, letteratura sulla, letteratura arte
letteratura greca » literatura graeca, letteratura fra, literatura grega
la letteratura » la litterature, la literatura, e letteratura
groups diels » groups fields, groups does, groups field
groupse die » group die, groupware die
i groups » 2 groups, 1 groups, 3 groups
air e » air en, air a, air 3

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: (( i groups ((air e) OR (air _)) letteratura greca ) OR ( i ((groupse die) OR (groups diels)) la letteratura sarda )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( i groups ((air e) or (air _)) letteratura greca ) or ( i ((groupse die) OR (groups diels)) la letteratura sarda ))".
• Adding a wildcard symbol may retrieve word variants: (( i groups ((air e) or (air _)) letteratura greca ) or ( i ((groupse die) OR (groups diels)) la letteratura sarda ))*.