Depending on which citation style you are using, you will need to differentiate between print and online copies. Each style has its own rules for formatting this information.
For example, you might need to include the online database where you retrieved the information. Including a URL of a journal or website can be appropriate for some citations. Many online sources now include a Digital Object Identifier (DOI) for the text. A DOI is a unique identifier assigned to the online content in order to locate that content on the Internet.
**URLs and DOIs are not enough -
you must include the full bibliographic information for a citation to an electronic source**