Analysis of information sources in references of the Wikipedia article "Roman administration of Judaea (AD 6–135)" in English language version.
The division of Palestine into two provinces, Palestina Prima and Southern Palestine, later to be known as Palaestina Salutaris, took place in 357-358 [...] In 409 we hear for the first time of the three provinces of Palestine: Palaestina Prima, Secunda and Tertia (the former Salutaris)