Note Boolean searching only works from the Boolean Search page.
Boolean search allows you to specify complex expressions that describe your exact search criteria.
The website's default behaviour is to consider all the words in a search. If you want to specifically allow either one of several words, you can use the OR operator (note that you have to type 'OR' in ALL CAPS). Example:
railways OR railroads
will give you results that contain either the word railways or the word railroads, whereas a search for railways railroads (without the OR) will show results that include both railways and railroads in the same record. (The AND operator is the default, so you don't actually have to type it in.)
You can use parentheses to combine an OR search with another term. E.g.:
(railways OR railroads) AND canada
Terms you want to exclude
You can also use Boolean search to exclude records that you do not want. For example, you can search for J.R.R. Tolkien materials other than The Lord of the Rings:tolkien AND NOT rings
Parentheses can be used to combine Boolean search strings:
tolkien AND NOT (rings OR hobbit)