what limits did the author place on the study?
writers of articles rarely tackle big topics. there isn't enough room in an article to write a history of the world or discuss big issues. Articles are generally written to advance understanding only a little bit. It may be because the subject has never been looked at before or because no one would be able to read a larger work easily (like a student's thesis). An article usually focuses on a particular period,event,change,person,or idea and even then may be limited even more.
this may be signifìcant if the author is trying to make generalizations about what he or she has discovered. Knowing something about education in the 1940s in Yellowknife may not tell you anything about education anywhere else or at any other time.
A more general discussion of subsistence strategies over a longer period may have more general relevance.
A critique of the literature in a specific field may replace having to read number of books. With assigned readings,an article will most often be assigned as an example of a type of research as a source of quality information on a specific topic or because it summarizes a lot of other writing on a given subject.