^Galván, Javier A. They Do What? A Cultural Encyclopedia of Extraordinary and Exotic Customs from around the World. ABC-CLIO. 19 June 2014: 51. ISBN 9781610693424（英语）. Early Christians in this region believed that, during Walpurgis Night, evil powers were at their strongest, and people had to protect themselves and their livestock by lighting fires on hillsides.