PRAGUE (AP) — František Janouch, a Czech nuclear physicist who set up a foundation in Sweden while in exile to support the dissident movement in his communist homeland at the time, has died. He was 92.

The Charter 77 Foundation said Janouch died on Friday morning in Sweden’s capital, Stockholm, where he had lived since the 1970s. No details about the cause of his death were given.

Born on Sept. 22, 1931 in the town of Lysa nad Labem near Prague, Janouch studied nuclear physics at Charles University in Prague and at universities in Moscow and St. Petersburg in the then Soviet Union.

As a leading expert in his field, he worked in a senior position at the Nuclear Physics Institute of the Czechoslovak Academy of Sciences and was professor at Charles University.

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After the 1968 Soviet-led invasion crushed a period of liberal reforms in Czechoslovakia known as the Prague Spring and the country was taken over by a hard-line communist regime, Janouch was fired from the institute and banned from lecturing.

At the invitation of the Royal Swedish Academy of Sciences, he moved to Sweden in 1974. He was stripped of his Czech citizenship and became a Swedish citizen in 1979.

In December 1978, he established the foundation to support those in Czechoslovakia who signed the Charter 77 human rights manifesto co-drafted by then dissident Václav Havel.

The signatories of the manifesto faced harsh persecution from communist authorities.

Among its activities, Janouch’s foundation smuggled banned books to Czechoslovakia, and also equipment that made it possible for dissidents to publish books and other materials by banned authors.

After the 1989 anti-communist Velvet Revolution led by Havel, the foundation moved to Prague and has been involved in various charity and other projects since then.

“František Janouch contributed significantly to the return of freedom to our country,” Prime Minister Petr Fiala said.