Using Boolean operators in combination
You can use multiple different Boolean operators in a search string to get a more specific results list.
Example
Using the search string:
tourism AND sustainability NOT Alaska
will return only results that include both tourism and sustainability, but don't mention Alaska.

Parenthesis
You can use parenthesis to help you make even more complex searches.
Example
Using the search string:
(tourism OR travel) AND sustainability
will return results that have either both tourism and sustainability or both travel and sustainability.
