DOIs or "digital object identifiers" are unique strings of letters and numbers that identify an article. 

DOI's are used as an "address" for an article.  DOIs can be found on the first page of an article, either at the top or the bottom.

They can also be found in a database record.  Not all articles have DOIs, but if your article does have one, you need to include it at the end of your citation.

Make sure you omit the UVM proxy from the DOI:

Correct: https://doi:10.1108/09513570310492290

Incorrect:  https://doi[-org.ezproxy.uvm.edu/]10.1108/09513570310492290