Diels-Kranz Numbering System
The written works of the Presocratic Philosophers have not survived. What little we know of their writings are fragments quoted in the works of later authors. These quotations, along with reports about the Presocratics and imitations of their works, were first compiled into a standard edition (Die Fragmente der Vorsokratiker) in the nineteenth century by the German philologist Hermann Diels (1848-1922). Later editions incorporate corrections and revisions to Diels' work that were made by Walther Kranz and other editors. Thus, the corrected and revised edition became known as the Diels-Kranz (DK) book; this work constitutes a complete edition of all the extant writings of Presocratic authors. The Diels-Kranz book has become a standard in the field of ancient philosophy. The works of Presocratics, therefore, are normally referred to by "DK numbers." In Diels-Kranz, each author is assigned a number, and within that author's number, entries are divided into three groups labeled alphabetically:
a. Testimonia: ancient accounts of the author's life and doctrines.
b. Ipsissima Verba: purportedly the exact words of the author.
c. Imitations: works which take the author as a model.
Within each of these three groups, individual fragments are assigned sequential numbers. For example, since Heraclitus is the 22nd author in Diels-Kranz, the third ipsissima verba quotation concerning him would be referred to as DK22b3.
Reference: See Die Fragmente der Vorsokratiker, by Hermann Diels and Walther Kranz (published 1985).