exile. Because possession of the manuscript incurred the risk of a long prison sentence for "anti-Soviet activities", Solzhenitsyn never worked on the manuscript in complete form. Since he was under constant KGB surveillance, Solzhenitsyn worked on only parts of the manuscript at any one time, so as not to put the full book into jeopardy if he happened to be arrested. For this reason, he secreted the various parts of the work throughout Moscow and the surrounding suburbs, in the care of trusted friends. Sometimes when he was purportedly visiting them on social calls he actually worked on the manuscript in their homes. During much of this time, Solzhenitsyn lived at the dacha of the world-famous cellist Mstislav Rostropovich, and due to the reputation and standing of the musician, despite the elevated scrutiny of the Soviet authorities, Solzhenitsyn was reasonably safe from KGB searches there. Solzhenitsyn did not think this series would be his defining work, as he considered it journalism and history rather than high literature. With the possible exception of One Day in the Life of Ivan Denisovich, it is his best-known and most popular work, at least in the West. Finished in 1968, The Gulag Archipelago was microfilmed and smuggled out to Solzhenitsyn's main legal representative, Fritz Heeb of Zürich, to await publication; a later paper copy, also smuggled out, was signed by Heinrich Böll at the foot of each page to prove against possible accusations of a falsified work. Solzhenitsyn was aware that there was a wealth of material and perspectives about Gulag to be continued in the future, but he considered the book finished for his part. The royalties and sales income for the book were transferred to the Solzhenitsyn Aid Fund for aid to former camp prisoners. His fund, (The Russian Social Fund), which had to work in secret in its native country, managed to transfer substantial amounts of money towards helping former gulag prisoners in the 1970s and 1980s. Reception and impact Beginning in 2009, Russian schools issued the book as required reading. Russian president Vladimir Putin called the book "much-needed", while the Russian Ministry of Education said that the book showed "vital historical and cultural heritage on the course of 20th-century domestic history." Arseny Roginsky, then head of the human-rights organization Memorial, welcomed Putin's backing for the Solzhenitsyn textbook. Natalya Reshetovskaya described her ex-husband's book as "folklore", telling a newspaper in 1974