## Boolean operators

MRS uses an implicit AND for multiple search terms. To create more complex queries you can enter boolean operators. The operators supported are AND (&), OR (|) and NOT (!). You can also combine terms using parenthesis. Please note that the operator names should be in upper case.

Parenthesis are also supported, i.e. you can now group boolean expressions together in more complex expressions.

To find both 'lysosyme' and 'lysozyme'
  Enter the query `'lysosyme OR lysozyme'`
To find all records containing lysozyme but excluding the EST records from EMBL.
  Enter the query `'lysozyme AND NOT kw:est'`
  (EMBL records have a keyword EST for all EST records, we use this to search the separate kw index. See Searching a specific field for more information on indices).
To find both lysosyme and lysozyme and also exclude the EST records
  Enter the query `'(lysosyme OR lysozyme) AND NOT kw:est'`