Complex sentence: Justin or Marcus Junianus Justinus or Justinus Frontinus was a 3rd century Roman historian, and the leader of a group of Christian gnostics who was criticised by the late 2nd and early 3rd century writer Hippolytus.
Split into simpler sentences: Justin or Marcus Junianus Justinus or Justinus Frontinus was a 3rd century Roman historian. Justinus was also the leader of a group of Christian gnostics who was criticised by the late 2nd and early 3rd century writer Hippolytus.