How to contact researchers who publish behind the paywall via Pubmed

For those readers not familiar with PubMed, articles (or at least abstracts and sometimes links to the authors email address) can be found by using this format:

https://www.ncbi.nlm.nih.gov/pubmed/?term=27839864

or if you are already at PubMed, pasting the PMID (PubMed IDentification) number, ex. 27839864, into the text search field. Most entries have a link at the top right to take you to the article

http://www.cell.com/cell/abstract/S0092-8674(16)31443-X

which may or not be open access. I note that academics at well funded research Universities / academic Medical Centers usually have this access paid by their institution, which is usually getting it from their indirect overhead money, which in the U.S. is mostly from NIH grants, such that taxpayers pay the bills but cannot easily read the article ... if the authors paid for both the peer review process and open access page charges, everyone could read all the useful scientific literature without direct charge.