The phrase "article form" refers to a written piece of work that is published online or in a magazine, newspaper, or blog. It usually consists of a specific topic or subject and follows a structured format. Full definition
It means that writing essay history you should read articles form journals and magazines, books, publications and interviews. (customwritingservices.org)
Zappalà's article forms part of Global Affairs» special Forum on «The European Union and Armed Drones», essential reading for anyone with an interest in the topic, and the first collection of articles on the European dimension of this new form of warfare. (sciencedaily.com)