Who directed 'Aliens' (1986)?

In what year was 'Grease' released? Who directed 'Saturday Night Fever' (1977)? In what year was 'Saturday Night Fever' released? In what year was 'Alien' released? In what year was 'Blade Runner' released? Who directed 'Gladiator' (2000)? In what year was 'Gladiator' released? Who directed 'The Martian' (2015)?