Unusually among the Olympic deities, Apollo had two cult sites that had widespread influence: Delos and Delphi. In cult practice, Delian Apollo and Pythian Apollo (the Apollo of Delphi) were so distinct that they might both have shrines in the same locality. Apollo's cult was already fully established when written sources commenced, about 650 BCE. Apollo became extremely important to the Greek world as an oracular deity in the archaic period, and the frequency of theophoric names such as Apollodorus or Apollonios and cities named Apollonia testify to his popularity. Oracular sanctuaries to Apollo were established in other sites. In the 2nd and 3rd century CE, those at Didyma and Clarus pronounced the so-called "theological oracles", in which Apollo confirms that all deities are aspects or servants of an all-encompassing, highest deity. "In the 3rd century, Apollo fell silent. Julian the Apostate (359 - 61) tried to revive the Delphic oracle, but failed."