It is quite possible that you will not find suitable citation templates for certain sources. Not all possible publication types are taken into account in the "Recommendations for the preparation of theses (in German)".
 

In this case, you must create a customised source citation and pay attention to the following points:

• The source citation should contain all important information. What information is important? There is no one-size-fits-all answer to this question, but you should make it as easy as possible for readers to find the publication. The tips below can help you to distinguish the important information from the unimportant.
• The citation should follow the basic principles of citation style (e.g. according to the recommendations of the Institute of Geography, the year of publication always comes after the author's name) and be consistent with the other citations.
• To make it clear in the citation what type of publication it is, you can add a description in square brackets after the title of the source, e.g. [dataset], [software] or [cereal box].
  
  

Tips:

• Look at different templates for your citation style - monograph, essay, internet address, etc. - and use the components that seem relevant for your citation.
• Take inspiration from other citation styles. The APA (American Psychological Association) citation style, for example, offers numerous citation templates, even for less frequently cited source types such as ethics codes and unpublished university theses. The book Cite Them Right also provides citation templates for many different types of resources.

(Earth Sciences Library, 2024)