The most common Boolean operators are AND, OR, and NOT. These can be used to refine or expand your search so that you retrieve just the right articles. We will be going over this in more depth in class but here's the basics:

OR - always expands your search (a good mnemonic is remember that OR = MORE). Use this for synonyms.

AND - always contracts your search by making it more picky (All articles you return should have both concept 1 & concept 2.

NOT - excludes articles containing this concept. So if I search for (Diabetes Mellitus Therapies NOT insulin), I would be telling the database not to include any articles with the word insulin in the title or abstract. Be careful using the NOT Boolean operator!  It's very easy to eliminate articles you would want to see!