The Codex Gregorianus and the Codex Hermogenianus were unofficial compilations. (The term "Codex" refers to the physical aspect of the works, being in book form, rather than on papyrus rolls. The transition to the codex occurred around AD 300.)[4] The Codex Theodosianus was an official compilation ordered by Theodosius II.[4] In February 528, Justinian promulgated the Constitutio Hac quae necessario, by which was created a ten-man commission to review these earlier compilations as well as individual laws, eliminate everything unnecessary or obsolete, make changes as it saw fit, and create a single compilation of imperial laws in force.[5] The commission was headed by the praetorian prefect, John of Cappadocia[6] and also included Tribonian, who was later to head the other Corpus Juris Civilis projects.[7]