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Citing

Citing sources is one of the fundamental principles of academic work. Quotations serve to substantiate and illustrate one’s own statements or working hypotheses and to place them within a research context. To distinguish one’s own ideas from those of others and to avoid intellectual property theft (plagiarism), quotations must be clearly marked with precise source references so that readers of the work can consult the sources themselves. The legal basis for citing is Section 51 of the German Act on Copyright and Related Rights (Urheberrechtsgesetz).

On this page, we would like to provide you with a brief overview of this topic. Please also consult the resources offered by your department or chair on this topic and inquire there about any specific guidelines (e.g., required citation style).

Different ways of using sources

Sources may either be quoted verbatim or paraphrased.

In the case of direct quotations, the text passage is taken verbatim from a source. The quotation is placed in quotation marks to separate it from your own thoughts.

  • Example:

    "Citations are cross-references to bibliographical information outside the current document [...]." (Mittelbach/Fischer 2023, p. II-469)

In paraphrases, other people's thoughts are reproduced in your own words. Phrases such as "According to author XY..." or "Author XY claims..." can also help to distinguish other people's thoughts from your own.

  • Example:

    Mittelbach and Fischer state that citations (in a LaTeX document) refer to external sources. (Mittelbach/Fischer 2023, p. II-469)

Citation styles

There are many different citation styles. Depending on the citation style selected, the result looks different. A rough distinction can be made between in-text and footnote styles. The scope of the information can also differ: in some styles, the bibliographic information is output in author-date format, for example, while in others it is output as a number that refers to the full entry in the bibliography.

The citation style can be determined, for example

  • by the supervisor of the work or by the department/chair etc. (if you are a student)
  • by the conference, journal, etc. in which you publish (if you are a researcher)

The following examples[1] illustrate different principles of citation styles.

In-text citation styles

With in-text citations, the source is named in brackets directly after the quotation in the text. This can be done in author-date format or using numbers, for example.

In the author-date format, the author's surname and the year of publication (as well as the page number) are listed.

  • Example:

    "Citations are cross-references to bibliographical information outside the current document […]." (Mittelbach/Fischer 2023, p. II-469)

With the numeric format, each cited source is assigned a number in the bibliography. After the quotation, the respective number of the source from which it is taken (and the page number) is then given in brackets.

  • Example:

    "Citations are cross-references to bibliographical information outside the current document [...]." (1, p. II-469)

    Bibliography
    1. MITTELBACH, Frank, and Ulrike FISCHER. The LaTeX Companion. Third Edition – Part I & Part II. Boston: Pearson, 2023.

In the alphanumeric style, each source is assigned an identifier (e.g. made up of the first letters of the surname and the last two digits of the year of publication). The bibliography then contains the complete bibliographic information.

  • Example:

    "Citations are cross-references to bibliographical information outside the current document [...]." [MiFi23, p. II-469]

    Bibliography
    [MiFi23] MITTELBACH, Frank, and Ulrike FISCHER. The LaTeX Companion. Third Edition – Part I & Part II. Boston: Pearson, 2023.

Footnote citation styles

In footnote styles, the reference is moved to a footnote at the bottom of the page. The footnotes are numbered so that the respective citation can be assigned to the source.

In a full citation, the complete bibliographic details of the source (including the number of the page containing the quote) are given in the footnote. This is usually the case for the first citation from a source.

  • Example:

    "Citations are cross-references to bibliographical information outside the current document [...]."1

    ____________
    1 MITTELBACH, Frank, and Ulrike FISCHER. The LaTeX Companion. Third Edition – Part I & Part II. Boston: Pearson, 2023, p. II-469.

If the same source is quoted several times in a document, the complete bibliographic information is no longer given in the footnote. Instead, the source is cited according to the author-date format or author-title format in a short reference.

  • Example:

    "Citations are cross-references to bibliographical information outside the current document [...]."2

    ____________
    2 MITTELBACH/FISCHER. The LaTeX Companion, p. II-469.

Bibliographic information (bibliography)

The complete bibliographical details of a source are given in the bibliography (or in the full citation). Which information is required depends on the chosen citation style on the one hand and on the respective document type on the other. For example, different information is required for an collective work than for a journal article.

Below we have listed some example citations[2] of the most common types of scientific publications.

  • Definition:
    a self-contained, coherent work written by one or more persons
  • Example:
    MAIBACH, Meike, Diagnostische Performanz und Einschätzungen von Primarstufen-Studierenden: Vergleich des informativen und zur Exploration anregenden Zugangs der digitalen, fallbasierten Lernplattform ‚FALEDIA‘ [online]. Wiesbaden: Springer Fachmedien. [Accessed on: February 24, 2026]. ISBN 978-3-658-50683-4. Available at: https://doi.org/10.1007/978-3-658-50683-4
  • Note:
    When citing, it is important to specify the respective edition (if available).
  • Definition:
    an individual section in a monograph
  • Example:
    MAIBACH, Meike, 2026. Digitale Lerngelegenheiten in der universitären Lehrkräfteausbildung. In: MAIBACH, Meike, Diagnostische Performanz und Einschätzungen von Primarstufen-Studierenden: Vergleich des informativen und zur Exploration anregenden Zugangs der digitalen, fallbasierten Lernplattform ‚FALEDIA‘ [online]. Wiesbaden: Springer Fachmedien. pp. 97-140 [Accessed on: February 24, 2026]. ISBN 978-3-658-50683-4. Available at: https://doi.org/10.1007/978-3-658-50683-4_3
  • Note:
    Usually, you do not need to cite a chapter of a monograph separately; the page number is sufficient. However, if, as in the example, there is a DOI or other identifier specifically for the individual chapter, you can cite it separately. In this case, the parent work (the monograph) is named in the citation (similar to chapters in a collective work).
  • Definition:
    a work published by one or more persons that brings together several individual contributions / chapters by different authors on an overarching topic
  • Example:
    MOORMANN, Peter and Nicolas RUTH (eds.), 2023. Musik und Internet: Aktuelle Phänomene populärer Kulturen [online]. Wiesbaden: Springer Fachmedien Wiesbaden. [Accessed on: March 26, 2026]. Musik und Medien. ISBN 978-3-658-39144-7. Available at: https://link.springer.com/10.1007/978-3-658-39145-4
  • Note:
    When citing, it is important to specify the respective edition (if available).
  • Definition:
    an individual contribution in a collective work
  • Example:
    MOORMANN, Peter, 2023. Populäre Musik im Sog digitaler Plattformlogiken: Musikbasierte Kürzestvideos am Beispiel der „Wipe It Down“-Challenge auf TikTok. In: Peter MOORMANN and Nicolas RUTH (eds.), Musik und Internet [online]. Wiesbaden: Springer Fachmedien Wiesbaden. pp. 99-110. Musik und Medien. [Accessed on: March 26, 2026]. ISBN 978-3-658-39144-7. Available at: https://link.springer.com/10.1007/978-3-658-39145-4_6
  • Note:
    When citing, it is important to name the parent work (collective work).
  • Definition:
    a contribution in a journal; usually assigned to an issue and volume in the journal
  • Example:
    KERKHOFF, Jana, Dominik BORRMANN and Gabriele SADOWSKI, 2025. Co-sorption of volatile components in polymer-based pharmaceutical formulations. Fluid Phase Equilibria. February 1, 2025. vol. 589, art. no. 114247 [accessed on: February 24, 2026]. Available at: https://doi.org/10.1016/j.fluid.2024.114247
  • Note:
    When citing, it is important to state the journal, volume and issue (if available) as well as the page number or alternatively the article number (if available).
  • Definition:
    e.g. a blog post or a contribution/part of a website; generally not a scientific source, its content may change
  • Example:
    SCHNEIDER, Anne, 2026. Iran-Krieg: Ein Friedensplan und Verhandlungen - was ist dran? tagesschau.de [online]. 2026. [Accessed on: March 26, 2026]. Available at: https://www.tagesschau.de/ausland/asien/trump-nahost-plan-100.html
  • Note:
    When citing, it is important that the date of access is given in case the page changes afterwards or disappears completely. It is best to keep a screenshot of the page.

Persistent identifiers

Most current scientific publications are also published electronically. However, it can happen that a work is only available in printed form (e.g. due to its age). The ISBN (= International Standard Book Number) is a persistent identifier for print media. Whether the ISBN is given in a citation or in the bibliography depends on the chosen citation style. The situation is similar with identifiers for electronic media (DOI, eISBN etc.). Whether an access date is given for DOI (= Digital Object Identifier) etc. also depends on the citation style. Only for a URL, the access date always has to be given.

If a persistent identifier is available, this is preferred to the conventional URL in the citation, as this only indicates the location of the document. As this can change, persistent identifiers are usually assigned for current publications. DOI is the most common electronic persistent identifier. URN (= Uniform Resource Name) and Handle can also be used, especially in repositories. If only a URN or Handle (or URL) is available, include this in the citation, otherwise include the DOI.

Reference management programs

Reference management programs simplify citing sources properly by automating it: quotations and references can be transferred to the desired location in the word processing program with one click; citations and a bibliography are generated at the same time using the selected citation style.

At TU Dortmund University, we offer training in the reference management programs Citavi and Zotero. Both provide more than 10,000 citation styles. Check whether the desired style is listed in the database of the respective program. If you are not looking for a specific style, you can also filter by citation method, language and subject area. In Citavi, you can do this via the menu item Citation - Citation style - Browse citation styles - Find and add style; in Zotero via Edit - Settings - Cite - Get additional styles.

Notes

[1] The examples are based on a graphic on the systematics of citation methods from Swiss Academic Software GmbH: https://www1.citavi.com/sub/manual6/en/index.html?citationstylelistdialogex.html (last accessed on 15.05.2026)

[2] The citations are based on the standard ISO 690. This standard is compatible with various citation styles.