The "literature" that is reviewed is the collection of publications (academic journal articles, books, conference proceedings, association papers, dissertations, etc) written by scholars and researchers for scholars and researchers. The professional literature is one (very significant) source of information for researchers, typically referred to as the secondary literature, or secondary sources. To use it, it is useful to know how it is created and how to access it.
The "Information Cycle"
The diagram below is a brief general picture of how scholarly literature is produced and used. Research does not have a beginning or an end; researchers build on work that has already been done in order to add to it, thus providing more resources for other researchers to build on. They read the professional literature of their field to see what issues, questions, and problems are current, then formulate a plan to address one or a few of those issues. Then they make a more focused review of the literature, which they use to refine their research plan. After carrying out the research, they present their results (presentations at conferences, published articles, etc) to other scholars in the field, i.e. they add to the general subject reading ("the literature").
Research may not have a beginning or an end, but researchers have to begin somewhere. As noted above, the professional literature is typically referred to as secondary sources. Primary and tertiary sources also play important roles in research. Note, though, that these labels are not rigid distinctions; the same resource can overlap categories.
Work backwards. Usually, your research should begin with tertiary sources:
Publishing the Literature
There are a variety of avenues for scholars to report the results of their research, and each has a role to play in scholarly communication. Not all of these avenues result in official or easily findable publications, or even any publication at all. The categories of scholarly communication listed here are a general outline; keep in mind that they can vary in type and importance between disciplines.
Peer Review - An important part of academic publishing is the peer review, or refereeing, process. When a scholar submits an article to an academic journal or a book manuscript to a university publisher, the editors or publishers will send copies to other scholars and experts in that field who will review it. The reviewers will check to make sure the author has used methodologies appropriate to the topic, used those methodologies properly, taken other relevant work into account, and adequately supported the conclusions, as well as consider the relevance and importance to the field. A submission may be rejected, or sent back for revisions before being accepted for publication.
Peer review does not guarantee that an article or book is 100% correct. Rather, it provides a "stamp of approval" saying that experts in the field have judged this to be a worthy contribution to the professional discussion of an academic field.
Peer reviewed journals typically note that they are peer reviewed, usually somewhere in the first few pages of each issue. Books published by university presses typically go through a similar review process. Other book publishers may also have a peer review process. But the quality of the reviewing can vary among different book or journal publishers. Use academic book reviews or check how often and in what sources articles in a journal are cited, or ask a professor or two in the field, to get an idea of the reliability and importance of different authors, journals, and publishers.
Informal Sharing - In person or online, researchers discuss their ongoing projects to let others know what they are up to or to give or receive assistance in their work. Conferences, listservs, and online discussion boards are common avenues for these discussions. Increasingly, scholars are using personal web sites to present their work.
Conference Presentations - Many academic organizations sponsor conferences at which scholars read papers, display at poster sessions, or otherwise present the results of their work. To give a presentation, scholars must submit a proposal which is reviewed by those sponsoring the conference. Unless a presentation is published in another venue, it will likely be difficult to find a copy, or even to know what was presented. Some subject specific indexes and other sources list conference proceedings along with the author and contact information.
Conference Papers / Association Papers / Working Papers - Papers presented at a conference, submitted but not yet accepted for publication, works in progress, or not otherwise published are sometimes made available by academic associations. These are often not easy to find, but many are indexed in subject specific indexes or available in subject databases. Sometimes a collection of papers presented at a conference will be published in a book.
Journals - Articles in journals contain specific analyses of particular aspects of a topic. Since journal articles can be written and published more quickly than books, academic libraries subscribe to many journals, and the contents of these journals are indexed in a variety of sources so others can easily find them, researchers commonly use articles to report their findings to a wide audience. Thus journals are also a good readily available source for current information on a topic.
Books - Books take a longer time to get from research to publication, but they can cover a broader range of topics, or cover a topic much more thoroughly, than articles or conference presentations. University press books typically go through some sort of a peer review process. There is a wide range of review processes (from rigorous to none at all) among other book publishers.
Dissertations/Theses - Graduate students working on advanced degrees typically must perform a substantial piece of original work, and then present the results in the form of a thesis or dissertation. Usually, only the library and/or department at the school where the work was done has copies of the dissertation, though especially significant ones are often collected by other libraries.
Web sites - In addition to researchers informally presenting and discussing their work on personal web pages, there are an increasing number of peer reviewed web sites publishing academic work. The rigor, and even existence, of peer reviewing can vary widely on the web, and it can be difficult to determine the reliability of information presented on the web, so always be careful in relying on a web-based information source. Do your own checking and reviewing to make sure the web site and the information it presents are reliable.
Reference Sources - Subject encyclopedias, dictionaries, and other reference sources present brief introductions to or summaries of the current work in a field or on a topic. These are typically produced by a scholar and/or publisher serving as an editor who invites submissions for articles from experts on the topics covered.
How to Find the Literature
Just as there are many avenues for the literature to be published and disseminated, there are many avenues for searching for and finding the literature. There are, for example, a variety of general and subject specific indexes which list citations to publications (books, articles, conference proceedings, dissertations, etc). The Wesleyan Library web site has links to the library catalog and many indexes and databases in which to search for resources, along with subject guides to list resources appropriate for specific academic disciplines. When you find some appropriate books, articles, etc, look in their bibliographies for other publications and also for other authors writing about the same topics. For research assistance tailored to your topic, you can sign up for a Personal Research Session with a librarian.