Perhaps you should try some spelling variations:
de investigaciones » de investigacion, la investigacion
e investigacion » de investigacion, en investigacion, la investigacion
pacis studies » species studies, pacific studies, packet studies
estudios e » estudios de, estudios en, estudios y

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: (( de estudios e investigacion ) OR ( ((pacis estudios) OR (pacis studies)) de investigaciones )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( de estudios e investigacion ) or ( ((pacis estudios) OR (pacis studies)) de investigaciones ))".
• Adding a wildcard symbol may retrieve word variants: (( de estudios e investigacion ) or ( ((pacis estudios) OR (pacis studies)) de investigaciones ))*.