Eevee's Eighth Evolution, Sylveon, Is the Newest Pokémon Announced for “Pokémon X” and “Pokémon Y”!, Game News

Pokémon X and Pokémon Y are planned to release simultaneously worldwide this October.

Pokémon News Archive, page 20

Sylveon Reveal! - Pokemon X and Y

Y (Adventures) - Bulbapedia, the community-driven Pokémon encyclopedia

Pokémon X and Y's New Eeveelution Revealed - IGN

Pokémon X & Y Video Confirms Eevee's New Evolution - Interest - Anime News Network

Sylveon Pokémon: How to catch, Moves, Pokedex & More

Brand-New Pokémon Type Confirmed? - My Nintendo News

Even More New Pokémon Revealed From Pokémon X and Y - Nintendojo Nintendojo

Eeveelution, Pokémon Wiki

Pokémon X and Y games