Under the Rule 18 of the Bluebook, authors require the use and citation of traditional printed sources when available, unless there is a digital copy of the source available that is authenticated, official, or an exact copy of the printed source. Generally, the Bluebook encourages authors to find and use the hardcopy of the sources. However, if the researchers cannot find the hard copies of the materials they should use the most current internet materials.
Generally, the Bluebook establishes three general formats for structuring a citation. These three general formats are (1) citations to the hard-copy print material, (2) citations that combine the print citation with the electronic citation using “available at,” and (3) citations directly to the electronic version.
Under the Internet Citations [Rule 18.2], authors should cite directly to an internet source when a source does not exist in a traditionally printed form or commercial database. Also, if the internet has a source exactly the same as the printed version and it would improve access, they may parallel cite to the internet with "available at. Besides that, the author should cover the following elements :
(1) Typeface the title or party name as you would for a normal citation. Do not underline the URL. If there is no printed comparison, treat the source as unpublished and follow rule 17. See generally rule 18.2.3(b).
(2) If an author is unclear, a title alone may be used [rule 18.2.3(c)].
(3) Only pinpoint cite, if a page number appears in the document itself, e.g. PDFs, and not screen numbers [rule 18.2.3(d)].
(4) Dates. Indicate a year if the date clearly refers to the material cited, else use "last visited X date " in the parenthetical [rule 18.2.3(e)].
Note: Authors should use dates that refer clearly to the material cited. Otherwise, authors should use " last updated, last modified, or las visited date.
Example: Faith Karimini, What Jeff Sessions Said about Russia Ties during Confirmation Hearings (last updated, March 3, 2017), available at http://www.cnn.com/2017/03/02/politics/russia-jeff-sessions-confirmation-hearing/index.html.