I have a book on the old Roman law (Twelve Tables) citing a Greek source for a detail on the bankruptcy/execution law. It is named "Dion." but I did not find a fitting work of a "Dionysius" or similar. There is no list of abbreviations in the book. It is possible, that the source deals with other ancient but not Roman law, as the author cites on the same page the Gospel of Matthew (Mt 18, 24).
The book is: Voigt, Moritz, Die XII Tafeln. Geschichte und System des Zivil- und Kriminal- rechts wie -prozesses der XII Tafeln nebst deren Fragmenten, reprint of the edition Leipzig 1883, Bd. 2, Aalen 1966. On page 360 is the citation:
Dion. VI, 26: διαλῦσαι μου τὸ χρέος οὐκ ἔχων, ἀπήχθην δοῦλος ὑπὸ τοῦ δανειστοῦ σὺν τοῖς υἱοῖς δυσίν
There are also citations of Dion. VI, 29 and 37 on the pages around. If it helps, I can write them off too.
Have you any idea who "Dion." could be and out of which work the citation is?