Question: In pre-Roman Gaul the Belgic tribe of the Veliocasses or Velocasses controlled a large area in the lower Seine valley, which retains a trace of their name, as the Vexin, in 52 they raised 3000 men to support which son of Celtillus the Avernian, leader of the Gallic tribes?
{'answer': 'Vercingetorix', 'supporting_facts': [['Veliocasses', 2], ['Vercingetorix', 0]]}