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

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 de investigacion )).
• Adding a wildcard symbol may retrieve word variants: (( de estudios e investigacion ) or ( pacis estudios de investigacion ))*.