Spanish club Barcelona and German team Schalke 04 have each celebrated Thursday Turkey's national day on Facebook.Barcelona shared a photograph on their Facebook page showing the Turkish flag, as well as Barcelona stars Lionel Messi, Neymar and Gerard Pique with three children wearing Barcelona scarves."Happy April 23. We are celebrating the April 23 National Sovereignty and Children's Day for all kids in the world," the message accompanying the picture read in Turkish.Meanwhile, German football club Schalke 04 also wrote on Facebook: "Wish you happy National Sovereignty and Children's Day" with a picture of German goalkeeper Ralf Fahrmann and a Turkish flag in the caption.