Arkady (1925-1991) and Boris (1931-2012) Strugatsky began to collaborate in the early 1950s after Arkady had studied English and Japanese and worked as a technical translator and editor, and Boris was a computer mathematician at Pulkova astronomical observatory. The Encyclopedia of Science Fiction describes them as 'the best Soviet SF writers' and works such as Hard to be a God, Definitely Maybe, The Snail on the Slope and Monday Begins on Saturday are powerful and poignant novels that continue to amaze and move readers. Andrei Tarkovsky's much admired film, Stalker, was based on their most famous work, Roadside Picnic.