Perhaps you should try some spelling variations:
economics agent » economics agents, economic agent, economics agency
recherche land » recherche dans, recherche und, recherche prend
economic rent » economic rents, economic report, economic trends
e recherche » de recherche, en recherche, et recherche
studi e » studi per, studia ve, studie 2

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "studi e recherche land ((economics agent) OR (economic rent)) ;~".
• Adding a wildcard symbol may retrieve word variants: studi e recherche land ((economics agent) OR (economic rent)) ;*.