Perhaps you should try some spelling variations:
28 institutions » 2.8 institutions, 25 institutions, 26 institutions
18 institutions » 1 institutions, 11 institutions, 13 institutions
8 institutions » 3 institutions, 1 institutions, 4 institutions

Try widening your search to All Fields.

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: %22associations%((((28 institutions) OR (18 institutions))) OR (8 institutions))%29 etc %_ bolivia%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%22associations%((((28 institutions) OR (18 institutions))) or (8 institutions))%29 etc %_ bolivia%22".
• Adding a wildcard symbol may retrieve word variants: %22associations%((((28 institutions) OR (18 institutions))) or (8 institutions))%29 etc %_ bolivia%22*.