Perhaps you should try some spelling variations:
de letteratura » e letteratura, di letteratura, de litterature
de litteratura » de litterature, de literatura, e letteratura
la letteratura » la litterature, e letteratura, di letteratura
la literatura » la litterature, a literature
grund libro » und libro
grunde die » grunde der, grunde des, grundlage 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 ((grund libro) OR (gran libro)) ((de letteratura) OR (de litteratura)) fra ) OR ( i grunde die ((la letteratura) OR (la literatura)) sarda )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( i ((grund libro) or (gran libro)) ((de letteratura) or (de litteratura)) fra ) or ( i grunde die ((la letteratura) OR (la literatura)) sarda ))".
• Adding a wildcard symbol may retrieve word variants: (( i ((grund libro) or (gran libro)) ((de letteratura) or (de litteratura)) fra ) or ( i grunde die ((la letteratura) OR (la literatura)) sarda ))*.