Complex sentence: The warning was passed through the channels existing at the time the information system "Ring", also appeared on the tapes of news official (full text in "Russia-XXI", № 8,1993).
Split into simpler sentences: The warning was passed through the channels that existed at the time: the information system "The Ring". It also appeared on the tapes of official news (full text in "Russia-XXI", № 8,1993).