Periodicals come in a variety of styles and are published for a variety of audiences.
They offer news, opinion, commentary, scholarly analysis, literary criticism, and reports of research. They range from brief newsletters published by trade organizations to in-depth journals published by scientific societies and university presses. All periodicals are published at more or less regular intervals, from daily newspapers to semi-annual journals. You must make active choices about the types of periodicals needed for a given research project. Magazines may be appropriate for some purposes, journals of opinion for others, but usually the most important sources for university-level research are academic journals.