Remember to use both English and the language of the site. Some search engines are so powerful that often you get good results with a minimum number of keywords. They may have been removed completely, or has its name changed, or be temporarily unavailable. These operators were named after the mathematician George Boole who invented them. He used the operators AND , OR and NOT to express logical processes.
Boolean logic represents a fundamental principle in searching information.
The means by which the terms used to describe the search topic are combined in a logical relationship. This means you can use Boolean expressions to combine your search terms in a way that will give you relevant results. The AND Operator Use the Boolean Operator AND between two search items in your search when you wish to combine search terms and to narrow your search results. The AND operator requires that both search terms be in the same record. For example, the search statement Methane and Mines retrieves just those records containing both methane and mines .