You can learn a lot by looking for similarities and differences among the sources you read. For example, you might identify a group of authors who take a similar approach to an issue, such as favoring increased government support for wind energy. You could then contrast this group with other groups of authors, such as those who believe that market forces should be the primary factor encouraging wind power and those who believe we should focus on other forms of energy. Similarly, you can make note of information in one source that agrees or disagrees with information in another. These notes can help you build your own argument or identify information that will allow you (and potentially your readers) to better understand the issue.