The Boolean Expression: can help you build more powerful searches by giving you tools called Boolean operators to influence how our software evaluates your request. ("Boolean" honors George Boole, a 19th-century British mathematician who suggested that logical thought could be expressed as algebra. As you'll see below, it seems logical.)
NOTE: When entering your search queries, Boolean operators such as AND are not case-sensitive; we've put them in ALL-CAPS for emphasis. You can use caps or lowercase when you type them in.
Be Specific with AND, OR, NOT
AND. Joining search terms with the AND operator tells that you want to find documents containing each term. (For example, Lithuania AND environmental AND energy) This is identical to selecting "All the Words" in the drop-down menu. But, as you'll see below, AND can be used in conjunction with other operators for more powerful searching. You can also use the "+" sign directly in front of words that you want included in your results. For example, "Lithuania+environmental+energy"
OR. Use OR when any of the search terms joined by the operator should appear in the results. This is similar to selecting Any of the Words in the drop-down menu. (For example, energy OR environmental.) Like AND, OR can be used as a building block of more-complex Boolean expressions.
NOT. Use the NOT operator to exclude unwanted documents when your search uses a term commonly found in connection with an unrelated topic, for example energy NOT environmental.
Quotation Marks " ". Put quotation marks around a group of words and you've got a phrase. This is like selecting The Exact Phrase in the drop-down menu. However, using quoted phrases in conjunction with other Boolean operators offers additional flexibility. Try to use "Energy production" AND Lithuania