Rule 16.6(f) in the 20th edition of the BlueBook (2015) addresses the citation of newspapers. The Rule states:
Internet and online newspapers.
Online newspapers may be used in place of print newspapers. Cite to the online source directly in accordance with rule 18.2.2. Pagination can be included if available but is not necessary. If the time of posting is available, include it in the parentheses in accordance with rule 18.2.2.
The sources below are useful for locating various local and national newspapers from around the country.