“02.10. 69. The Office for Foreign Assets Control of the Treasury Department issued a Note stating that it had reasons to believe that the nickel sulphate produced in the USSR could be wholly or partly made with or derived from nickel of Cuban origin. It was communicated that as from October 3, 1969, nickel sulphate imports made directly or indirectly from the USSR would be detained by Customs until their release from Customs or other provision were authorized by the Office for Foreign Assets Control, under the provisions of the Cuban Assets Control Regulations.” [Pro Embargo]

“Lyndon B.Johnson (D). Timeline,” Cuba versus Blockade: Cuban People’s website, 2007