Since the introduction of the European accessibility act, which aims to improve the accessibility of products and services, the EPUB format has been preferred to the PDF format as the standard for the online provision of e-books. Several e-book providers such as Ebook Central (Proquest) point out this change in recent reports, as it has an impact on the use of e-books in their portals.

What is problematic about this?

EPUB files adapt flexibly to screen sizes and fonts. The disadvantage: there are no fixed page numbers in the documents. In science, however, page numbers are required in many citation guidelines in order to make citations retrievable. In this blog article, we explain how to cite from EPUBs despite the lack of page pagination.

Screenshot of a “page view” of an EPUB e-book in Ebook Central. The “page number” at the bottom right can vary.

What alternatives are there to specifying pages?

What to do if the EPUB format does not provide fixed pages? There are various alternatives for referencing citations from EPUB files:

• Chapter or section numbers (e.g. chapter 3, paragraph 4)
• shortened versions of chapter or section headings
• Percentages or positions (e.g. 45%, 1654 loc for Kindle readers)

What do the official handbooks say?

If you look at the relevant manuals, you will find rules on how to cite in continuous text or footnotes and how to create bibliographies. We show some examples here. However, deviations are possible in individual cases, as even the handbooks leave room for interpretation in places.

What else should be considered when referencing e-books?

If possible, a DOI or (nondatabase) URL with access date should always be linked in order to make the source clearly traceable. In general, the DOI is preferable to the URL in the citation context, as it never changes and always refers to the same target object. If there is only one URL and this URL links to a source in a commercial database behind a paywall, it can be replaced by the name of the database (e.g. ProQuest Ebook Central) according to some regulations. However, the APA guidelines explicitly state that the name of a database may be omitted if the sources can also be found elsewhere (e.g. on another platform).

Some citation guidelines recommend specifying the format of the e-book reader used, such as Kindle or EPUB, when citing from e-books that are accessed without a URL on an e-reader, an e-reader app or on a computer with e-reader software.

Where can I find more information?

For all those who want to delve deeper: The most important citation standards provide helpful information – especially on detailed questions regarding the correct citation of e-books without page numbers. The current editions of the regulations can be found in the University Library collection:

• Publication Manual of the American Psychological Association (7th edition from 2020)
• Chicago Manual of Style (18th edition from 2024)
• Harvard (the exact application of the guidelines depends on the university and lecturer, we use the internationally used versions in Cite Them Right from 2022)
• MLA handbook (9th edition from 2021)
• IEEE Reference Guide (version V 3.28.2025 from 2025)

In addition, our MIKA e-learning module on Citation & Referencing provides a comprehensive overview of academic citing and referencing in general (it will be availabe in English soon). We are also happy to discuss all questions relating to citation and reference management with Zotero and Citavi in our personal “Book a Librarian” consultations.

As we have received a number of enquiries, we have compiled and illustrated the most important information on using the Nautos standards database in this blog post.

The previous blog post on switching from Perinorm to Nautos remains valid, of course.

Nautos, like Perinorm before it, can be accessed via our website. The databases are listed there under the menu item “Search & Find”.

The next click on “databases” takes you to DBIS, our database information system. All our licensed databases are listed there, sorted by subject. Nautos can be found in the category General/Interdisciplinary as well as in the subject areas Electrical Engineering, Measurement and Control Engineering, Mechanical Engineering, Materials Science, Production Engineering and some more. You can also search for the name of the database in the menu on the left.

Then there is a detailed description of Nautos as well as the “Link to the search” which, after a short info on the licence conditions, leads to the database. Nautos provides access to all standards with a DIN classification as well as the VDI standards.

In the database, the dashboard is displayed first. Here you will find current notes, version peculiarities (as Nautos is still in development) and useful tips for searching. On the left of the menu is the icon that leads to the search.

A special feature of this database is the Intelligent Search – Nautos can therefore provide useful results with the document number as well as with search terms. Below the search bar there are further search fields, for example to search only for currently valid standards or to link different search terms via the dynamic search.

Unfortunately, errors can still occur in the database – for example, documents that should be available in full text (visible by a blue puzzle symbol in the “Document” column) are not accessible or are not displayed at all. If you notice this, please let us know so that we can bring it to the attention of the Beuth publishers.