How is this suitable for my assignment?
Public documents must be assessed in the same way as other documents.
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When can I use a newspaper article?
In some cases, it might be relevant to include newspaper articles, for instance, to actualize your topic with quotes from public debate. They should, however, not be used as the main source, but as an example of how topics are conceived and described at a given moment.
If you are using newspapers as a historical source, you should note that older newspapers were often used as a channel for members of the social elite. Advertisements and announcements may have historical value.