Complex sentence: The account of the run near Marathon to Athens first appears in Plutarch's "On the Glory of Athens" in the 1st century AD, which quotes from Heraclides Ponticus' lost work, giving the runner's name as either Thersipus of Erchius or Eucles.
Split into simpler sentences: The account of the run from near Marathon to Athens first appears in Plutarch's "On the Glory of Athens" in the 1st century AD. Plutarch quotes from a lost work of Heraclides Ponticus and gives the runner's name as either Thersipus of Erchius or Eucles.