Perhaps you should try some spelling variations:
del investigationes » model investigations, cell investigations, gel investigation
de investigacion » la investigacion
los estudios » los estados, de estudios
estudios del » estudios de, estudio del, estudos de
seis estudio » seis estudios, el estudio, de estudio

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: (( los estudios del investigationes ) OR ( seis estudio de investigacion )).
• Adding a wildcard symbol may retrieve word variants: (( los estudios del investigationes ) or ( seis estudio de investigacion ))*.