Perhaps you should try some spelling variations:
groups studied » group studies, groups study
der filosofica » de filosofia, e filosofica, e filosofia
de literatura » de litterature, la literatura, y literatura
e literatura » y literatura, e literatur, a literatura
test groups » test group, test grounds, host groups
studied der » studie der, studien der, studies der

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: "test groups studied der filosofica ((e literatura) OR (de literatura))*".