On 23 July 1914, the Austro-Hungarian Minister of Foreign Affairs Leopold Count Berchtold (pictured) sent a coded telegram to the Austro-Hungarian Minister to Montenegro Herr Otto. In his telegram, Berchotld refers to the Austro-Hungarian ultimatum to Serbia.
Count Berchtold to Herr Otto. Vienna, 23 July 1914.
You are authorised to give His Majesty the King [of Montenegro] a copy of the circular note [i.e. the Austro-Hungarian ultimatum to Serbia] to the Powers in strict confidence, if he asks you for it. At the same time you can tell him that we are happy to assert that the results of the inquiry mentioned in the circular note does not in any way touch upon Montenegro.
Source: 1919 Austro-Hungarian Red Book, with minor edits.