Which preposition to use with reichsrath

at Occurrences 1%

of the population of which is Italian and all the rest Serb or Croat, preponderatingly Serb and Orthodox in the south and preponderating Croat or Roman Catholic in the north) was a province of Austria and sent deputies to the Reichsrath at Vienna; at the same time it was territorially isolated from Austria and had no direct railway connexion with any country except a narrow-gauge line into Bosnia.

Which preposition to use with  reichsrath