 In the late 1950s restrictions on literature were eased, and by the 1970s and 1980s, writers were increasingly ignoring official guidelines.Leading authors of the Soviet era include novelists Yevgeny Zamyatin (emigrated), Ilf and Petrov, Mikhail Bulgakov (censored) and Mikhail Sholokhov, and poets Vladimir Mayakovsky, Yevgeny Yevtushenko, and Andrey Voznesensky.The Soviet Union was also a major producer of science fiction, written by authors like Arkady and Boris Strugatsky, Kir Bulychov, Alexander Belayev and Ivan Yefremov.