Perhaps you should try some spelling variations:
federal institutes » federal statutes, federal statute, federal constitutions
chemical institute » mathematical institute, chemical constituents, chemical constitution
central institute » memorial institute, virtual institute, rural institute
federal institute » memorial institute, federal statutes, der institute

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: ((((((central institute) OR (federal institutes))) OR (federal institute))) OR (chemical institute)) of labour*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((((central institute) OR (federal institutes))) or (federal institute))) or (chemical institute)) of labour*".