"Twenty-first century." . . "Outer space" . . "Outer space." . "Time Travel Fiction" . . "Exploration of outer space." . . "Twenty-first century Fiction." . . "Human-alien encounters Fiction." . . "Science Fiction" . . . . . "Space"@en . "Space" . . . . "Science fiction" . "Science fiction"@en . . . . . . . . . . . . . "Electronic books"@en . . . . . . . . "Espace" . . . "Fiction"@en . "Fiction" . . . . . . . . . "Human-alien encounters." . .