Boolean Logic allows you to combine keywords to make a search more precise. The three terms are: AND, OR, NOT.
AND - Narrows a search
Example: electromagnetic radiation AND brain: Retrieves articles with both electromagnetic radiation and the brain.
OR - Expands a search
Example: electromagnetic radiation OR x-ray: Retrieves articles with just electromagnetic radiation, just x-ray, and articles with both electromagnetic radiation and x-ray.
NOT - Removes a term from a search
Example: electromagnetic radiation NOT x-ray: Retrieves articles with electromagnetic radiation, but remove all articles with any mention of x-ray. Use NOT sparingly because you often lose many useful articles.
