How can I use this?
Secondary Sources are useful for both gaining a broad knowledge of a topic area (e.g review papers), and for understanding how certain discoveries or projects were received by the scholarly community. They give you opinions, analysis, and a discussion of impact which you can use to place primary sources in context.
When other writers summarize or review the theories and results of original scientific research, their publications are known as Secondary Literature. These publication types serve to synthesize the findings to date and present the ideas to a wider audience. Examples of secondary literature include:
Secondary literature is not as current as the primary literature but it is often more descriptive and is useful for finding introductory material.
 Grodsky, G.M. 1970. Insulin and the pancreas. Vitamins & Hormones, 28: 37-101.