 The Effect is next mentioned in "Invasion of the Dinosaurs" (1974), where the Third Doctor states that it "tends to limit research into time travel" but, once again, he does not go into detail as to why.The novelisation of the story reveals that Blinovitch was a "great bear of a man from Russia" who had reversed his own timestream, reverting to infancy.The next time the Effect is mentioned on-screen is in "Mawdryn Undead" (1983), but there it is not a scientific principle that prevents people from redoing their actions (for whatever reason).