The text search engine allows queries to be formed from arbitrary Boolean expressions containing the keywords AND, OR, NOT, and grouped with parentheses. 

For example:

procedure codes

finds documents containing 'procedure' and 'codes'

procedure OR codes

finds documents containing 'procedure' or 'codes'

procedure AND codes

finds documents containing both 'procedure' and 'codes'

procedure AND NOT codes

finds documents containing 'procedure' but not 'codes'

(procedure AND NOT codes) AND physician

finds documents containing 'physician', plus 'procedure' but not 'codes'

auth*

finds documents containing words starting with 'auth' (i.e., authorizing, authorized, authorize)