Characteristics of citation index

① Citation index overcomes the shortcomings of traditional subject index and classification index that it is sometimes difficult to select subject words or classification numbers, and provides a convenient and practical retrieval approach. (2) There is no need for subject analysis to look up the thesaurus or classification table when indexing, which is convenient for computer automatic processing. (3) Citation index has some shortcomings, such as incomplete literature, too large space, and sometimes missing detection due to unreliable citations.