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APA – Citing Sources

Missing reference information

It might happen that the information needed to create a reference is missing from the source. In that case, try to look for the source in a library catalogue. If you're lucky, the catalogue will provide you with the missing information. If not, APA has strategies to adapt the reference.

Read more about citing sources with information missing: Missing reference information

Unknown author

If there is no author, the reference begins with the work's title. Alphabetize the reference entry by the first significant word of the title (i.e. leave out "A, "An", and "The" at the beginning of titles).
Though, consider first whether the author of the work is a group or an organization. 

  • Scientific principles. (2021).

No date

If no date is given, use the abbreviation n.d. within parenthesis (= no date).


Johnson, A. (n.d.) The book. A publisher.

Several sources without year of publication

If you have several sources without year of publication, the sources are separated by adding a, b, c, etc. after n.d.
Please note that there is a hyphen between n.d. and the letter:

  • Anderson, T. (n.d.-a). Algebra from the past. Cambridge University Press.
  • Anderson, T. (n.d.-b). Mathematical journeys through time. Cambridge University Press.

In the reference, references with no date precede references with dates. 

Anderson, T. (n.d.)
Anderson, T. (2020)