The use of bibliographic citation is a crucial aspect in the creation and dissemination of information. Numerous studies have been done ranging from simple citation counts to more complex bibliographic coupling studies, and from citation classifications to citation motivation studies. This review focusses on the citation studies that have explored the complexities and the underlying norms of the citation process. The major emphasis is placed upon the studies which have dealt with citation functions, citation quality, citation concepts and citation motivation. The international perspectives of citation practice are also discussed.