• Research articles - These are your standard scientific articles.  Most often published in peer-reviewed journals, primary research articles report on the findings of a scientist's work.  They will almost always include a description of how the research was done and what the results mean.
• Review articles - Published in peer-reviewed journals, but seek to synthesize and summarize the work of a particular sub-field, rather than report on new results. Can provide helpful background information. Learn how to find them on the Advanced Search tab.
• Preprint articles - Preprints are versions of journal articles that are in the process of being peer-reviewed. Some authors and databases share these documents as examples of extremely current research. However, since these articles haven't gone through the peer review process, they should evaluated especially carefully.
• Editorials/Opinion/Commentary/Perspectives – An article expressing the author's view about a particular issue. These articles can be well researched and include a lot of citations to the peer reviewed literature, or simple items without citations, but are not themselves peer reviewed.
• Trade publication articles - These publications are often aimed at professionals (doctors, brewers, teachers) or particular disciplines.  Articles in these publications may be several pages long and include a few references, but they are usually summarizing research published in other publications or reporting on industry news.  These can be helpful for keeping up with your discipline or finding a research topic.
• News – Science news articles can be found in a wide variety of publications.  Popular newspapers and magazines, trade publications and scholarly publications can all have science news articles.  These articles often will refer to a recent study published as a primary research article.
• Blog posts - 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.
• Technical Reports – Government agencies and NGOs often do scientific work.  The reports they produce are not often peer reviewed, but can be an important part of the scientific literature.
• Dissertations/Theses – These are the final products that result from research conducted for a PhD or a Masters degree. While they undergo exhaustive review by academic advisers and committee members, most disciplines don't consider them peer-reviewed since the review follows different processes.

This information is adapted from Bonnie Swoger's "Types of Scientific Literature" and Khue Duong's "Preprints & E-prints".

State extension units often provide excellent education or research information.  One way to find extension publications is to use the Google Advanced search.  Limit your search to just .edu sites and then include "extension" as one of your keywords along with your topic.  This should just provide extension publications in your results list.

If you want to just search OSU Extension publications, you can look in the OSU Libraries ScholarsArchive.  Use the advanced search to limit to just "Extension & Experiment Station Communications".