Primary Research Articles: A primary research article reports on an empirical research study conducted by the author(s). It is typically always published in a peer-reviewed journal. Terms to look for in these type of articles as clues are: analysis, study, investigation, examination, experiment, numbers of people or objects analyzed, content analysis, or surveys.
Pre-Print / Post-Print: A pre-print is a full draft research paper that is shared publicly before it has been peer reviewed. Most preprints are given a digital object identifier (DOI) so they can be cited in other research papers. A post-print is a digital draft of a research journal article after it has been peer-reviewed and accepted for publication, but before it has been typeset and formatted by the journal.
Trade Publication Articles: These types of articles contain news, current events information, articles, and ads of interest to people in that industry or profession. Unlike scholarly journals, trade publications do not contain original research. Their focus is on current trends and issues. (secondary source)
News: This type of source can provide insights that might not be covered in scholarly sources. For instance, news sources are excellent for finding out people’s reactions, opinions, and prevailing attitudes around a new scientific discovery. Popular newspapers and magazines, trade publications and scholarly publications can all have science news articles. These types of articles often will refer to a recent study published as a primary research article. Whether news sources are good for your assignment depends on the research question.
Blog Posts: A blog is a personal or professional website that is updated frequently and displays opinions, as well as routinely links to other sources. To identify a blog, look for the presence of multiple posts and information that is personal, anecdotal, or opinion-based discussing daily research, science policy or even life in academia. Blogs can be a great way to get involved in the scientific community, and many scientific blog posts can point you back to the peer reviewed literature.
Article Comments (formal, reviewed): These are a criticism of a published journal article that is submitted as a formal comment. These short pieces are reviewed by editors or possibly peer-reviewers. Also, since almost every journal is online, a link to a formal comment is often included on the site for the original article.
Technical Reports: Reports produced by government agencies and non-profits can be an important part of the scientific literature. TRs are not peer-reviewed unless they are subsequently published in a peer-review journal. A TR citation will include a report number and will probably not have journal or publisher information. They might contain data, design criteria, procedures, literature reviews, research history, detailed tables, illustrations/images, explanation of approaches that were unsuccessful.
Other Gray Literature: The term “gray literature” largely refers to items that are distributed or published outside of the traditional journal and book publishers. Examples of gray literature are government reports, policy statements and issues papers, conference proceedings, pre-prints and post-prints of articles, theses and dissertations, research reports, geological and geophysical surveys, maps.
Conference Proceedings – long papers: Other than journal articles, conferences are the second major form of formal communication among scientists. Typically this involves a group of professional scientists gathering to present findings about their research. These papers can be published in book form in a volume referred to as the “Proceedings of Conference X.” Sometimes these papers go through peer-review, and sometimes they do not.
Conference Proceedings – abstracts: More often, the research presented as posters or PowerPoint presentations at a conference won’t have a formal write up published after the fact. Occasionally the scientists will archive a copy of their presentation on a website, but most often the only record of the presentation will be the brief description (abstract) of their presentation that the scientists submitted to the conference organizers. These abstracts can be found in search engines and scholarly databases.
Books: Most scientific books cannot be considered "primary research". In general, they describe and interpret the primary research published in scholarly journal articles.
Maps: Thematic maps focus on a particular theme or subject (i.e. weather, population, density, or geology). They can be published as stand alone publications, supplements to journal articles or books, or parts of technical reports from government agencies or non-profits. Scientific thematic maps often include several pages of prose describing the methods used to create the maps, the data that inform the results, and the interpretations that result from the data.
Dissertations / Thesis: A research project completed as part of an undergraduate or postgraduate degree allowing students to present their findings in response to a question or proposition.