The Bluebook requires citation to printed material (provided it is available), unless there is an authenticated, official, or exact digital copy of the printed sources. See R. 18.2.1
Example: The Ohio Supreme Court has designated the Supreme Court website as the Ohio Official Reports for opinions of the courts of appeals and the Court of Claims. See Ohio Rep. Op. R. 3.2, http://www.supremecourt.ohio.gov/LegalResources/rules/reporting/Report.pdf [https://perma.cc/772J-5ALP]. These opinions are in PDF format and bear a watermark.
If there is no print format or if the print format is obscure and is, for all practical purposes unavailable, cite to the most stable Internet source available.
Eric Goldman, When Should Search Engines Ignore Court Orders To Remove Search Results?,Tech. & Marketing L. Blog (Sept. 4, 2013), http://blog.ericgoldman.org/archives/2013/09/when_should_sea.htm [https://perma.cc/U2AN-2TXE].
Bill Ong Hing, Understanding SB1070 from the Lens of Institutionalized Racism and Civil Rights, Legal Services N. Cal.: Race Equity Project, http://www.equity.lsnc.net/understanding-sb1070-from-the-lens-of-institutionalized-racism-and-civil-rights (last visited Sept. 9, 2015).
The 21st Edition of The Bluebook Rule 18.2.1(d) states:
“Archiving of Internet sources is encouraged, but only when a reliable archival tool is available. For citations to Internet sources, append the archive URL to the full citation in brackets” – the rule includes the following example:
Letter from Rose M. Oswald Poels, President/CEO, Wis. Bankers Ass’n, to Elizabeth M. Murphy, Sec’y, SEC (Sept. 17, 2013), http://www.sec.gov/comments/s7-03-13/s70313-178.pdf [http://perma.cc/B7Z7D9DJ].
Perma.cc is also the example used to demonstrate the archived sources rule in the Rule 18.1 Basic Citation Forms for Internet Sources table on page 179:
Rocio Gonzalez, Puerto Rico’s Status Debate Continues as Island Marks 61 Years as a Commonwealth, Huffington Post (July 25, 2013, 9:00 AM), http://www.huffingtonpost.com/2013/07/25/puerto-rico-status-debate_n_3651755.html [http://perma.cc/C6UP-96HN].
A parallel citation to an Internet source may be provided if it substantially improves access to the source. Follow the regular rules for citing the source and then add the parallel Internet citation.
Commission on Women in the Profession, American Bar Association,From Visible Invisibility to Visibly Successful: Success Strategies for Law Firms and Women of Color in Law Firms (2008), http://www.americanbar.org/content/dam/aba/migrated/wome/woc/VisiblySuccessful.authcheckdam.pdf.
D. Andrew Austin & Mindy R. Levit, Cong. Research Serv., The Debt Limit: History and Recent Increases (Aug. 27, 2013), http://fpc.state.gov/documents/organization/213995.pdf [https://perma.cc/RM46-46PS].
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