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An Introduction to The Bluebook

Overview

Rule 4 governs the general use of the short citation forms id., supra, and hereinafter. Many source types have additional rules that supplement or override Rule 4. Refer to the table at the beginning of Rule 4 to identify exceptions.

Id.

Rule 4.1 addresses the use of id. (short for idem, meaning "the same"). Use id. when citing the immediately preceding authority, either:

  • within the same footnote, or
  • in the footnote directly above, provided that footnote includes only one authority. 

When citing to the same authority but a different page, use id. at [new page].

Source Example(s) Explanation
The same authority as in the immediately preceding footnote, which contains only one authority
  1. Johnson v. Phelan, 69 F.3d 144, 145 (7th Cir. 1995).
  2. Id.
  1. Franklin A. Gevurtz, Building a Wall Against Private Actions for Overseas Injuries: The Impact of RJR Nabisco v. European Community, 23 U.C. Dᴀᴠɪs J. Iɴᴛ'ʟ L. & Pᴏʟ'ʏ 1, 2 (2016).
  2. Id. at 15. 

Under Rule 4.1, id. may be used when citing the same authority as the immediately preceding footnote, as long as that footnote contains only one authority. In the first example, both footnotes cite page 145 of Johnson v. Phelan.

In the second example, "Id. at 15" is used to cite a different page of the same article cited in the immediately preceding footnote. Pinpoint citations are permitted after id. to direct the reader to a specific page. 
The same authority as in the immediately preceding footnote, which contains multiple authorities
  1. Johnson v. Phelan, 69 F.3d 144, 145 (7th Cir. 1995); Timm v. Gunter, 917 F.2d 1093 (8th Cir. 1990).
  2. Johnson, 69 F.3d at 145. 
  1. Hannah L. Buxbaum, The Scope and Limitations of the Presumption Against Extraterritoriality, 110 AJIL Uɴʙᴏᴜɴᴅ 62, 63 (2016); see also Gevurtz, supra note 17, at 3.
  2. Buxbaum, supra note 20, at 64.

Id. may only be used when the immediately preceding footnotes cites a single authority. If the footnote includes multiple sources, the use of id. is not allowed. The reference would be ambiguous.

In these examples, the preceding footnotes cite more than one authority; therefore, you must use:

  • A short-form citation for cases (see Rule 10.9); or

  • Supra for secondary sources (see Rule 4.2), as in Buxbaum, supra note 20.
The same authority more than once in a single footnote
  1. Pamela Laufer-Ukeles, Collaborative Family-Making: From Acquisition to Interconnection, 64 Vɪʟʟ. L. Rᴇᴠ. 223, 223 (2019). Laufer-Ukeles observes that "domestic adoption involves a widely-accepted system of what is considered 'non-commercial adoption,' even including private adoption . . ." Id. at 238.

Id. may be used within the same footnote to refer back to a previously cited authority, as long as no other source has been introduced in the interim.

In this example, id. refers to the Laufer-Ukeles article already cited earlier in the same footnote. Because no other authority is introduced between the full citation and the use of id., this usage is permitted.

Supra

Rule 4.2(a) governs the use of supra.

Use supra to refer back to an authority that was previously cited in full in an earlier footnote, unless id. would be more appropriate. Supra is only permitted for certain categories of materials. 

Use supra for: Do not use supra for:
  • Legislative hearings
  • Court filings
  • Books
  • Pamphlets
  • Reports
  • Unpublished materials
  • Nonprint resources
  • Periodicals
  • Services
  • Treaties and international agreements
  • Regulations, directives, and decisions of intergovernmental organizations
  • Internal cross-references
  • Cases
  • Statutes
  • Constitutions
  • Legislative materials or debates (except hearings)
  • Restatements
  • Model Codes
  • Regulations

Short forms for cases, statutes, and legislative materials or debates (other than hearings) and provided in their respective rules.
Source Example(s) Explanation
An authority previously cited in full, but not in the immediately preceding footnote

1. William Baude & Stephen E. Sachs, The Law of Interpretation, 130 Hᴀʀᴠ. L. Rᴇᴠ. 1079, 1107-10 (2017).

10. Baude & Sachs, supra note 1, at 1136.

5. Rocky Mountain National Park Act § 1, 16 U.S.C. § 191. 

7. U.S.C. § 191. 

In the first example, footnotes 1 and 10 refer to the same law review article, a source type that permits the use of supra under Rule 4.2(a). Once an authority has been cited in full, you may refer back to it using supra in a later footnote, even if it's not the footnote directly above.

In the second example, footnotes 5 and 7 refer to a federal statute. Supra is not permitted for statutes per Rule 4.2(a). Instead, Rule 12.9 requires an appropriate short form. Statutes, like cases and constitutions, follow separate short-form rules and never use supra for cross-referencing.

Hereinafter

Rule 4.2(b) governs the use of hereinafter. This short form is used in the first full citation of an authority to assign a shortened name to a long or complex title. Insert the word hereinafter and the shortened form in brackets directly after the citation and before any explanatory parentheticals.

For example, hereinafter may be used to reduce confusion when:

  • the authority has a long or complex title, or
  • multiple sources in the same footnote need to be distinguished.

In later citations to the same authority, use the assigned short form followed by a comma and the relevant supra reference. 

Note: Hereinafter follows the same use restrictions as supra. For a list of authority types where use is not permitted, see the chart above.

Scenario Example(s) Explanation
Assigning a shortened name to an authority with a long or complex title

1. Protocol Additional to the Geneva Conventions of 12 August 1949, and Relating to the Protection of Victims of International Armed Conflicts (Protocol I), June 8, 1977, art. 10 [hereinafter AP I].

10. AP I, supra note 1. 

 When a source has a long or technical title, Rule 4.2(b) allows you to assign a short name using hereinafter in brackets after the full citation. This makes later references shorter and clearer. Once assigned, the short name is used in subsequent citations, followed by an appropriate cross-reference (here, supra) to the original footnote.
Distinguishing between multiple authorities by the same author in a single footnote

3. Lisa Pruitt, Who's Afraid of White Class Migrants? On Denial, Discrediting, and Disdain and Toward a Richer Conception of Diversity, 31 Cᴏʟᴜᴍ. J. Gᴇɴᴅᴇʀ & L. 196, 197 (2015) [hereinafter White Class Migrants]; Lisa Pruitt, Welfare Queens and White Trash, 25 S. Cᴀʟ. Iɴᴛᴇʀᴅɪsᴄ. L.J. 289, 290 (2016) [hereinafter Welfare Queens].

4. Pruitt, White Class Migrants, supra note 3, at 198.

 When citing multiple sources by the same author in a single footnote, hereinafter helps avoid confusion in later footnotes. Without it, a later citation like “Pruitt, supra note 3” would be ambiguous. Assigning short names makes each source distinct and ensures precise cross-referencing.