Landmark articles are centrally important because they've reported a breakthrough, insight, or new idea of great importance within that research topic. Landmark studies change our understanding of a topic, and form the canon of works important to a topic.
Landmark articles are also called core, pivotal, classic, core, or seminal works.
These landmark articles are referred to time and time again in the research--they are cited frequently.
When writing an annotated bibliography, it is important that you try to identify and include landmark articles in your work.
Identifying landmark articles will take some work on your part. They...
Image source: Public Domain, CIA.