See:
- Brendan Mac Gonagle, An Tríbhís Mhòr - On The Triskelion in Iron Age Celtic Culture - https://www.academia.edu/11899946/
- http://www.hradiska.sk/2012/04/oresany-slepy-vrch.html [Slovak]
See:
Oppidum Petit Celland
Neolithic Circular Enclosure. Rondel.
Marching camp