This chapter focuses on only one aspect of procedural law: that relating to citations, the process by which parties were summoned to appear before a court. It examines three specific parts of the law of citations. First is the question of its necessity. Did one have always to issue a formal citation before adjudication? Second is the question of time. How long an interval had to come between service of the citation and the required appearance in court? Third is the question of the citation's contents. How much information had to be placed in it to establish its validity? The task is to investigate how the ius commune came into being. The three topics chosen are important and are illustrative.