Citation Styles

How often do I cite?

  • Remember: one citation at the end of a string of sentences or a paragraph cannot “cover” the entire section.
  • Cite a source the first time it is used in each paragraph.
  • Every sentence thereafter in the paragraph that uses information from this same source must contain either a signal phrase or a citation clearly indicating where the information came from.
    • Note: always use a citation (even if you also use a signal phrase) every time you quote material.

In-text Citation Placement

Where in the sentence does my in-text citation go?

  • If you name your source(s) in a given sentence, a parenthetical citation containing only the year follows immediately after the name(s) of the author(s). Example: In contrast to earlier work by Abbott and Costello (1999), Laurel and Hardy (2008) propose an altogether different model for optimizing hat density.
    • If you quote a source that you have named in the sentence, the parenthetical citation gets split, with the page number(s) placed in parentheses immediately after the quoted material. Example: Schartz and Metterklume (2013), however, note that the Laurel–Hardy method produces "less than suboptimal millinerial outcomes" (p. 198) in the case of heavily laden peach-basket hats.
      • But compare what happens when the quotation comes first: The "less than suboptimal millinerial outcomes" reported by Schartz and Metterklume (2013, p. 198), however, continue to impede the development of sufficiently dense peach-basket hats.
  • If you do not name your source(s) in a given sentence, a single parenthetical citation goes at the end of the sentence or clause it covers (Goffman, 1974), inside the punctuation, like this (Melville, 1851).
    • If the sentence ends with a quotation, "close the quote, then place the citation between the quotation marks and the punctuation, like this” (Woolf, 1931, p. 14).
  • Do not insert spaces between a parenthetical citation and the punctuation that follows it.

In the paragraph below, the  parenthetical in-text citations are highlighted in yellow, and the signal phrases are in blue. Note that the second sentence is common knowledge, whereas the final sentence is clearly the opinion of the author.

Red and yellow are the best colors with which to decorate your restaurant because they induce feelings of hunger (Smith & Jones, 2009). Consider popular fast-food chains, which often use red and yellow in their advertising and décor. According to Smith and Jones’ study (2009), restaurant customers felt more energized in red and yellow environments, which encouraged them to order more food. The same study indicated that patrons felt relaxed in blue and purple environments, which encouraged them to “spend more time considering the menu options and eat at a slower pace” (p. 29). Although blue décor can give your restaurant a more casual, laid-back feel (Kramer, 1999)Smith and Jones believe it encourages patrons to linger at their tables without ordering additional food or beverages. Accordingly, it is difficult to identify a popular chain restaurant that decorates with calmer hues.


For more information, see the TPO's Citing Responsibly in APA (PDF).

Bibliography / List of References

What is the difference between them?

  • A Bibliography lists all works cited and consulted
  • A List of References includes all works cited in a text

The NPS Thesis Processing Office prefers a List of References for the following: 

  • Thesis
  • Capstone project report
  • MBA report
  • Dissertation

For papers, check with your professors for their preference.

Honorifics (Dr., Col., Professor, etc.)

Including these titles in the body of your document is acceptable; do not include them when citing.

Et al. / Multiple Authors of a Single Work

For examples of how to properly incorporate the citation into your text and references, see row one.

# Authors of a single work First citation
if in signal-phrase format
Subsequent citations First citation
if in parenthetical format
Subsequent citation Reference List


Walker (2007) reported that ...

Walker (2007) reported that ...

Your citation goes at the end of the sentence (Walker, 2007).

Your citation goes at the end of the sentence (Walker, 2007).

Walker, V. (2007). [then the remaining reference information]

Walker and Allen (2004)

Walker and Allen (2004)

(Walker & Allen, 2004)

(Walker & Allen, 2004)

Walker, V., & Allen, R. L. (2004).
Three, Four, or Five List all authors List just first author + "et al." List all authors List just first author + "et al." List all authors
Bradley, Ramirez, Soo, and Walsh (2006) Bradley et al. (2006) (Bradley, Ramirez, Soo, & Walsh, 2006) (Bradley et al., 2006) Bradley, K. S., Ramirez, H., Soo, T., & Walsh J. (2006).
Six or Seven Wasserstein et al. (2005) Wasserstein et al. (2005) (Wasserstein et al., 2005) (Wasserstein et al., 2005) List all authors. (2005).
Eight or More as above as above as above as above List first six authors, then insert (...) and finally add the last author's name. (2005).
Groups (readily identified through abbreviation) as authors National Institute of Mental Health (NIMH, 2003) NIMH (2003) (National Institute of Mental Health [NIMH], 2003) (NIMH, 2003) National Institute of Mental Health. (2003).
Groups (no abbreviation) as authors University of Pittsburgh (2005) University of Pittsburgh (2005) (University of Pittsburgh, 2005) (University of Pittsburgh, 2005) University of Pittsburgh. (2005).

 Adapted from American Psychological Association. (2010). Publication Manual of the American Psychological Association (6th ed.). Washington, DC: Author.

Acronyms: Organization as Author

Do not include acronyms with organizations listed as authors in the List of References.

Like this:

R: Department of Defense. (2005, December 19). Information assurance training, certification, and workforce management (DoD Directive 8570.01-M). Washington, DC: Author. Retrieved from


Not this:

R: Department of Defense (DoD). (2005, December 19). Information assurance training, certification, and workforce management (DoD Directive 8570.01-M). Washington, DC: Author. Retrieved from



Translations and Works Not in English

For works with a translator, follow the format for edited books but substitute "trans." for "ed." in the notes and "translated" for "edited" in the references:

R: Manqué, M. Old and rejected poems. (1989). Translated by Hickinson, P. Scituate, MA: Narrow Fellow Press.

For works in languages other than English, format the title in sentence case, then give the translation, also in sentence case, in square brackets immediately following:

R: Manqué, M. (1992).  "L'esthétique de l'échec" [The aesthetics of failure]. In Sweeney H. (Ed.), Éviter les clichés et des autres clichés [Avoiding clichés and other clichés], edited by Sweeney, H. 3–44. New Brunswick: Stew & Offspring.

Missing Info

If any information is missing from a source (a journal with no volume number, for example), simply omit that information. For sources consulted in hardcopy, omit the URL and any additional verbiage that introduces it. Anything retrieved online, however, MUST have a link. The only exception is journals retrieved from a subscription database such as ProQuest. 

Capitalization (Title Case / Sentence case)

Title Case: To Capitalize or Not: A Brief Tutorial


Sentence case: To capitalize or not: A brief tutorial

Note: Always format the information in your citations (titles, author names, etc.) according to the requirements of the citation style you are using, regardless of how it appears in the original source.

Page Numbers

For direct quotes, add page numbers to the in-text citation only.

Example: (Haynes, 2009, p. 70)

For book chapters, include page-number range in List of References/Bibliography.

Example: Cordesman, A. H., Mausner, A., & Kasten, D. (2009). Introduction. In J. Smith (Ed.), Winning in Afghanistan: Creating Effective Afghan Security Forces (pp. 1–12). Washington, DC: Center for Strategic and International Studies.

Print vs. Online

When citing a source retrieved online, use the "online" format even when you or someone else printed out the material. For example, if you print out a thesis or your advisor provides you with a printed thesis, it is still categorized as an online document.

Only cite as a print source when the material has been produced by a publisher in hard copy. For example, if you obtain a print journal or book from the library stacks, it is categorized as a printed source.

URLs: Retrieved from and Formatting

  • Only include date retrieved if the source material has no date.
  • Never include a period at the end of the URL.
  • Do not insert a hard or soft return within the URL string.
  • A URL does not belong in an in text-citation. Ever.

Author as Publisher

When the author and publisher are the same, use the word "Author" as the name of the publisher in the reference list citation.

Department of Defense. (2012, April 16). Identification (ID) cards required by the Geneva Convention (DOD Instruction 1000.01). Washington, DC: Author.

Same Author, Multiple Works / Multiple Sources in One Citation

Examples given are for books; follow the appropriate style for the source type you are citing.


Generic Example Actual Example

Same author, same year, different sources

  • List sources in alphabetical order by title in the List of References (ignoring initial "a," "an," or "the") and append a lowercase letter to the year.
Source 1

R: Author, A. A. (Year + a). Title of book in sentence case and italics. City, State: Publisher.

T: (Author, year + a)

R: Hawthorne, M. (2006a). The cannibal’s dilemma: An unnatural history of four siblings. New York, NY: Penguin.

T: (Hawthorne, 2006a)

Source 2

R: Author, A. A. (Year + b). Title of book in sentence case and italics. City, State: Publisher.

T: (Author, year + b)

R: Hawthorne, M. (2006b). Having people for dinner: A guide for the home cook. New York, NY: Penguin.

T: (Hawthorne, 2006b)

T: (Author year + a, year + b)

T: (Hawthorne 2006a, 2006b)

Same author, different year, different sources

  • List sources in chronological order.
Source 1

R: Author, A. A. (Year). Title of book in sentence case and italics. City, State: Publisher.

T: (Author, year)

R: Hawthorne, M. (2006). Having people for dinner: A guide for the home cook. New York, NY: Penguin.

T: (Hawthorne, 2006)

Source 2

R: Author, A. A. (Year). Title of book in sentence case and italics. City, State: Publisher.

T: (Author, year)

R: Hawthorne, M. (2008). Regrets. New York, NY: Penguin.

T: (Hawthorne, 2008)

T: (Author, year 1, year 2)

T: (Hawthorne, 2006, 2008)

Different authors, different years

  • Place references in alphabetical order and separate them with a semicolon. Ensure all authors appear in the list of references.

T: (Author 1, year; Author 2, year; etc.)

(Hawthorne, 2006b; Norton, 1998; Stulberg, 2014)

(Nekeip & Nywdlog, 2005; Qaga, 2007; Romato, Trange, & Bemon, 1995).


Secondary Sources

A secondary source is a source that cites some other work that you discuss in your text.

Whenever possible, consult primary sources and your sources’ sources yourself. Upon investigation of the primary source, you may find you disagree with the secondary source author’s analysis or methods. Only use secondary sources when the primary source is unavailable.

How to Incorporate Secondary Sources

The following passage incorporates a properly credited secondary source. The secondary source information is highlighted in yellow; the primary source information is highlighted in blue.

Walker (2008) describes data collected in 1999 by Miguel Roig that correlates students’ inadequate paraphrasing to poor reading comprehension. Citing Roig’s data, Walker explains that “students do in fact possess skills necessary for paraphrasing but … may be impeded from applying those skills when dealing with rigorous text” (p. 387).

Note: Include  only  the  secondary  source  (the  source  you  consulted)  in  your  reference  list.