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b. Logical AND

The logical AND is the class intersection operator. The result of logical AND between two classes is the class containing only those elements, which are common to both classes. Thus if A and B are two terms representing the two classes indexed with terms A and B respectively, the logical AND between these two classes is the class of documents indexed with both term A and term B. 

The logical AND therefore is used to narrow the scope of the result, requiring the co-occurrence of terms, and will in general decrease the number of hits. The symbol used to indicate the logical AND operation is the asterisk (*). Thus, for example, to retrieve documents about food with the term "Africa" in the title and written by Smith one could use the logical AND operators as follows: 

TI=Africa * A=Smith *  D=food$

Note that as for the logical OR, the order in which the terms are given is irrelevant. 

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