US calls Russia ‘manure salesmen’ over Moscow attack claims DW (English)The Moscow concert massacre was a major security blunder. What’s behind that failure? The Associated PressWhy Russia’s Vast Security Services Fell Short on Deadly Attack The New York TimesWhat A Missed Terror Warning Says About U.S.-Russian Ties And Putin’s Thinking Radio Free Europe / Radio LibertyUS says it warned Russia ‘in writing’ about threat before ISIS concert shooting in Moscow USA TODAY