Some resources require a more complicated approach to creating persistent links. Typically, these are scientific or medical resources, but exceptions may exist. Examples include The Journal of Chemical Education. These resources use what is called a DOI (Digital Object Identifier).
What is a Digital Object Identifier (DOI)?
Digital Object Identifiers work with a common prefix, similar to a proxy URL: http://dx.doi.org/
A DOI is a unique, registered link that will not change over time. The benefit of a DOI link is that it tends to be far shorter than links found in resources such as EBSCO databases and other similar electronic resources.
This is a DOI found in the Journal of Chemical Education: 10.1021/ed5001922
Here is how that number can be used to generate a persistent link: