They can range from the selective (a very narrow area of research or only a single work) to the comprehensive (a larger amount or range of works).
They can also exist as part of a larger work or stand on their own.
At the end of the review is a conclusion that once again explicitly ties all of these works together to show how this analysis is itself a contribution to the literature.
So how do authors turn a network of articles into a coherent review of relevant literature?
These literature reviews are generally a bit broader in scope and can extend further back in time.
This means that sometimes a scientific literature review can be highly theoretical, in addition to focusing on specific methods and outcomes of previous studies.
It is not usually a linear process—authors often to go back and check the literature while reformulating their ideas.
This also means you will not be writing the literature review at any one time, but constantly working on it before, during, and after your study is complete.
One way to conceive of a literature review is to think about writing it as you would build a bookshelf.
You don’t need to cut each piece by yourself from scratch.