Perhaps you should try some spelling variations:
de letteratura » e letteratura, de litteratura, de litterature
di letteratura » e letteratura, de literatura, della letteratura
la literatura » la litterature, a literature
grunde fir » grunde fur, grunde der, grunde die

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 grunde fir ((de letteratura) OR (di letteratura)) sarda ) OR ( i grand livre ((y literatura) OR (la literatura)) de )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( i grunde fir ((de letteratura) or (di letteratura)) sarda ) or ( i grand livre ((y literatura) OR (la literatura)) de ))".
• Adding a wildcard symbol may retrieve word variants: (( i grunde fir ((de letteratura) or (di letteratura)) sarda ) or ( i grand livre ((y literatura) OR (la literatura)) de ))*.