The reason a comma is put in between the book titles is because, while they are in quotation marks, they are still part of a list. When listing things, you put a comma in between each item. For example, if you were to say “He likes bananas, oranges, and carrots”, you would have to put commas between each item that “He” is said to like. How these commas are placed is a matter of debate for some people, since many are starting to avoid using the Oxford comma. If you do not use the Oxford comma, the sentence would read “He likes bananas, oranges and carrots.”
In this section, you should explicitly address the issue of how scholars, including yourself, can handle the conceptual questions. This follows the previous point closely. What sources should scholars use and how should they use them? Do you put a preference in studying the French Revolution on the declarations made by revolutionaries, on their public debates, or on what happened ‘on the ground’, including the violent opposition they aroused? If you discuss the latter, you underline the fact that the Revolution led to civil war, and that the causes of what you present as the Revolution were not a mass rejection of the existing system. You also point out that in 1789 few people envisaged what they were expected to support in 1792 (a republic and the trial of the king) let alone 1793 (the Reign of Terror). The Revolution is thus presented and studied as a dynamic, changing process, which requires different explanations at particular stages.