 The Armenian SSR had boycotted the All-Union referendum, though Armenian sources allege that Baku had planned measures against the Armenians long before the referendum.Although the execution of Operation Ring was not proposed to Soviet officials until mid-April 1991, Mutalibov insisted in an interview that such plans had originally been formulated as early as 1989.Viktor Krivopuskov, who visited Karabakh in 1990, writes