Complex sentence: Case citation is a system used in many countries use to identify past court case decisions, either in series of books called reporters or law reports, or in a "neutral" style that identifies a decision regardless of where it is reported.
Split into simpler sentences: Case citation is a legal system component that many countries use to identify past court case decisions. These cases are documented either in a special series of books called reporters or law reports, or in a "neutral" style that identifies a decision regardless of where it is reported.