The citation method makes use of a so-called key publication. During the initial exploration for your research, you may have come across publications that are relevant to your subject. Or a lecturer or your supervisor may have drawn your attention to it. A key publication can be either a book or a journal article containing crucial information about (an aspect of) your subject. A key publication is also recognizable from the fact that it is cited in review articles. A review article is a publication in which the author examines the current state of research on a given research topic. Furthermore, a publication that comes up frequently in searches for literature on your subject may be taken as a key publication.