Premise: "Sei gesegnet ohne Ende" (English translation: "Be Blessed Without End"), also known as the ″Kernstock-Hymne″, is a German language song that was the national anthem of Austria from 1929 until 1938. Written by Ottokar Kernstock, it was sung to the famous tune of "Gott erhalte Franz den Kaiser" by Joseph Haydn that is also used for the "Deutschlandlied", since 1922 the national anthem of Germany.
Hypothesis: Haydn tunes were used for at least two European anthems.