What is a "Daud of Sons" as stated in Definition of Faith of the Council of Chalcedon? In my copy of Readings in World Christian History Volume 1: Earliest Christianity to 1453, edited by John W. Coakley &amp; Andrea Sterk, the 35th text, starting on page 175, entitled "Definition of Faith of the Council of Chalcedon", is a text regarding the Council of Chalcedon, and in it, the author says that "for it [Truth, as best I can tell] opposes those who would render the mystery of the dispensation [i.e. the Incarnation] in a Daud of Sons;" (emphasis mine)

My question is, what is a "Daud of Sons," and how would false teachers make the Incarnation into such a thing?

Here's a link to an online copy I found that seems to be the same translation
Definition of Faith of the Council of Chalcedon
I suspect it should read a 'duad of sons', not a 'daud of sons'. A duad is something made two parts. Compare it with triad or monad.

The Nestorian position is sometimes described as teaching that Christ is a duad, composed of a divine person and a human person. According to this, Jesus was not a single person who was fully man and fully God. Instead, the human son of Mary and the Divine Son of God, the Word, were closely connected but not united. (The nature of this connection differs depending on the version of Nestorianism.) In particular, Nestorius argued that Mary was the mother of the man Christ, but was not the mother of the Word. As such, he was accused of dividing Jesus into two persons, two sons.

The Chalcedonian position is that Christ is a single person with two natures. This unity is such that it is not possible to separate the actions and experiences of Jesus into human parts or divine parts. In opposition to Nestorius, they taught that Mary is the Theotokos, mother to the  Theanthropos Jesus, both human and divine.