Source: University of Auckland Library
In electronic bibliographic databases, you can use AND, OR, and NOT in Subject searches, which look for matches in the title, author, subject headings, and note fields of each catalog record. After identifying the most important concepts, it is necessary to indicate how the concepts should be linked with Boolean operators (AND, OR NOT). Various methods are used to combine the indexed terms in order to retrieve the desired result. The best known of these are logical operations, known as Boolean operators. It is also important to keep in mind that most Search Engines require that Boolean operators be typed in Capital letters