It sounds like you might be looking for a specific resource, perhaps a game, a PDF, or an educational guide related to the .
Such as PDF guides or eBooks detailing the history of the Roundheads and Cavaliers.
Because that phrase could refer to a few different things, could you clarify what you're after? For example, are you looking for:
There are several titles (like English Civil War by Ageod) that users often look for downloads of.
Free rulebooks or guides for playing out the battles with miniatures.