Citation patterns are also known to be affected by unethical behavior of both the authors and journal staff. Such behavior is called impact factor boosting, and was reported to involve even the top-tier journals. Specifically the high-ranking journals of medical science, including the Lancet, JAMA and New England Journal of Medicine, are thought to be associated with such behavior, with up to 30% of citations to these journals being generated by commissioned opinion articles.  On the other hand, the phenomenon of citation cartels is rising. Citation cartels are defined as groups of authors that cite each other disproportionately more than they do other groups of authors who work on the same subject. 
There is no uniform agreement on all of the details of a citation for information found on the Web or the Internet. Most suggestions for the form of a citation include the name of the author, the title of the work, the date the information was last revised, the date the information was accessed, and the URL. The date the information was accessed is included because it's relatively easy to modify information on the Web, and the information available through a URL sometime in the future may not be the same as when it was accessed for the research. Methods for determining the date when information on the Web and the title of a Web document are discussed.