Bulgaria–United States relations to work. Bulgaria became a member of the Warsaw Pact on May 14, 1955. Though no Soviet troops were stationed on Bulgarian soil, in 1968, Zhivkov sent a Bulgarian division to join Polish, Hungarian and Soviet troops to crush a popular uprising in Prague. In 1978, the Bulgarian secret police were implicated in the assassination in London of Georgi Markov, a Bulgarian dissident who was a correspondent for the BBC World Service, Deutsche Welle radio and the U.S. sponsored Radio Free Europe. Markov was assassinated with a poisoned umbrella on September 7, Zhivkov's birthday. The rise of democratic movements across
Ricin was charged with manufacturing ricin in his dorm room, as well as the intent of "[using] the ricin on another undergraduate student with whom he had a relationship". Mohammed Ali from Liverpool, England was convicted after attempting to purchase 500 mg of ricin over the dark web from an undercover FBI agent. He was sentenced, on 18 September 2015, to 8 years' imprisonment. Ricin Ricin ( ), a lectin (a carbohydrate-binding protein) produced in the seeds of the castor oil plant, "Ricinus communis", is a highly potent toxin. A dose of purified ricin powder the size of a few grains