depriving Grigorenko of Soviet citizenship on the ground that he was undermining the prestige of the Soviet Union. The 1970s marked a peak in the use of external exile as a punitive measure by the Soviet Union (as opposed to the internal type, which was highest between the mid-1930s and early 1950s); often the pattern was that a trip abroad for work or medical treatment was transformed into permanent exile. In the same year, Grigorenko became a U.S. citizen. Being in USA since 1977, Grigorenko took an active part in the activities of the Ukrainian Helsinki Group foreign affiliate. On 23 July 1978, Grigorenko made a statement condemning the trials of Soviet dissidents Anatoly Shcharansky, Aleksandr Ginzburg and Viktoras Petkus. In 1979 in New York, Grigorenko was examined by the team of psychologists and psychiatrists including Alan A. Stone, the then President of American Psychiatric Association. The team could find no evidence of mental disease in Grigorenko and his history consistent with mental disease in the past. Their findings were drawn up and publicized by Walter Reich. Grigorenko's case confirmed accusations, Stone wrote, that psychiatry in the Soviet Union was at times a tool of political repression. Petro Grigorenko described his life and views, and his assessment by Soviet psychiatrists and periods of incarceration in prison hospitals in his 1981 memoirs V Podpolye Mozhno Vstretit Tolko Krys… (In the Underground One Can Meet Only Rats…). In 1982, the book was translated into English by Thomas P. Whitney under the title Memoirs and reviewed by Alexander J. Motyl, Raymond L. Garthoff, John C. Campbell, Adam Ulam, Raisa Orlova and Lev Kopelev. In 1983, he said he considered the American political-economic system to be "the best that mankind has found to date." In 1983, a stroke he suffered left him partially paralyzed. Grigorenko died on 21 February 1987 in New York City. In 1991, a commission, composed of psychiatrists from all over the Soviet Union and led by Modest Kabanov, then director of the Bekhterev Psychoneurological Institute in St Petersburg, spent six months reviewing Grigorenko's patient files. They drew up 29 thick volumes of legal proceedings, and in October 1991 reversed the official Soviet diagnosis of Grigorenko's psychiatric condition. In 1992, an official post-mortem forensic psychiatric commission of experts met in Ukraine. They removed the stigma of being a mental patient and confirmed that there were no grounds for the debilitating treatment