The ethnogenesis of the Greek nation is linked to the development of Pan-Hellenism in the 8th century BC. According to some scholars, the foundational event was the Olympic Games in 776 BC, when the idea of a common Hellenism among the Greek tribes was first translated into a shared cultural experience and Hellenism was primarily a matter of common culture. The works of Homer (i.e. Iliad and Odyssey) and Hesiod (i.e. Theogony) were written in the 8th century BC, becoming the basis of the national religion, ethos, history and mythology. The Oracle of Apollo at Delphi was established in this period.