You've been searching the literature gathering documents -- lots of documents. Your file in a citation manager for this project is bulging and if you've printed out those documents, the pile is huge.
Here's some advice on how to manage all this reading material.
The following articles recommend ways to read and digest a research article ...
In your review you will need to "group" the literature that you've found. As you'll see in the next section, you can group by theme, method, topic, chronology, and other issues. To keep track of what each document says and which ones have similar information, create a literature matrix. The matrix will consist of a table, with each row representing a specific document. Each column in the table will represent different issues, topics, themes, etc. Once the table is filled out and you re-sort by the different columns, the patterns in the literature will stand out.
Here's some articles that show how to do a matrix.