There are thousands of medical journal articles and research papers on POTS, dysautonomia and related problems. If you are just looking for some basic introductory information, the following four journal articles provide you with the basic mechanisms of POTS and also some essential information on the various tests use to evaluate POTS and the underlying causes of POTS. I give copies of each of these articles to any new doctors I see. It is very important for them to understand POTS before making treatment decisions or changing my medications.
1) The Postural Tachycardia Syndrome: A Concise Guide to Diagnosis and Management
Co-authored by Dr. Blair Grubb, one of the leading experts on POTS, this article is a good introductory summary about POTS.
2) A Review of Postural Orthostatic Tachycardia Syndrome is also a good introductory summary, and has some different info not contained in Dr. Grubb's article.
3) Approach to the Evaluation of Small Fiber Peripheral Neuropathy and Disorders of Orthostatic Intolerance. This article from Mayo Clinic is the best I have found pertaining to the diagnosis and underlying causes of small fiber neuropathy, which is very common in POTS.
4) Renin-Aldosterone Paradox and Perturbed Blood Volume Regulation Underlying Postural Tachycardia Syndrome. This is from Vanderbilt University's acclaimed Autonomic Dysfunction Center. This article explains the role of low blood volume in POTS.
For additional medical literature on POTS, you can visit PubMed. PubMed is a service of the National Institutes of Health. Most major medical research in the US will be published on PubMed, or at least an abstract of the article. Many foreign research papers appear on PubMed as well. If you read the abstract and you decide that you want to read the full article and it isn't available on Pub Med, try typing the title of the article into Google to find a free full version. Also, when you view a research paper in PubMed, you will often see related journal articles listed on the top right corner of the screen. That is a good way to find even more info on the topic you are interested in.
Besides Pub Med, you can also search through individual medical journals. Sometimes private medical journals require a one time fee or a monthly subscription to view the article. Before you pay to read it, ask your doctor if they subscribe to that journal, or ask your local library if they can help you obtain a copy. Many public and university libraries subscribe to medical journals, and you may be able to do your research from their computers or connect in to their computer network from home.
Several medical journals that require a subscription fee make their content available for free one year after it has been published. Check out: http://www.freemedicaljournals.com/ Check out the individual journal's website to see if old issues are available for free.
When you find a POTS related journal article, there will usually be citations listed at the end of the article. Typing these citations into Google or looking for them on Pub Med usually leads you to the article that was cited, or at least an abstract of it.
The Dysautonomia Information Network (DINET) maintains a long list of POTS related research papers: http://www.dinet.org/research.htm However, the articles are not on the DINET website. DINET just has a list of citations.