 The rubrics, i. e. the summaries of the various titles, have the force of law, if they contain a complete meaning; on the other hand, the summaries of the chapters have not this juridical value.It is customary to quote these collections by indicating the number of the chapter, the title of the collection, the heading of the title, the number of the book and the title.The "Decretals" of Gregory IX are indicated by the letter "X", i. e. extra Decretum Gratiani; the "Sixth Book" or "Decretals" of Boniface VIII by "in VIº" i. e. "in Sexto"; the "Clementines" by "in Clem.