Witchery (Italian: La Casa 4, also known as Witchcraft and Ghosthouse 2) is a 1988 Italian horror film directed by Fabrizio Laurenti and starring David Hasselhoff, Catherine Hickland, Hildegard Knef, Linda Blair, and Annie Ross.
 It is the first sequel to "Ghosthouse", which itself is an "unofficial sequel" to "The Evil Dead".
Carnosaur 2 is a 1995 low budget sequel to "Carnosaur", and the second of the "Carnosaur" franchise.
 The film is about a team of scientists who go to a nuclear mining facility to investigate a possible meltdown and instead find a large number of cloned dinosaurs who have been hidden there after the events of the first film.
 "Carnosaur 2" was followed by a direct sequel titled "", and an unofficial sequel titled "Raptor".
Black Emanuelle 2 (Italian: "Emanuelle nera n° 2"), also known as "The New Black Emanuelle", is a 1976 Italian psychological drama-sexploitation film directed by Bitto Albertini.
 It is an unofficial sequel of "Black Emanuelle".
House of the Dead 2 (alternately titled House of the Dead II: Dead Aim) is a 2005 film and a sequel to the 2003 horror film, "House of the Dead".
 Based on the series of the same name, the film was directed by Michael Hurst and premiered at the Sitges Film Festival in Spain on October 14, 2005, and premiered in the United States on the Syfy on February 11, 2006.
My Sassy Girl 2 (Chinese: 我的野蛮女友2) is a 2010 Chinese romantic comedy film directed by Joe Ma and starring Lynn Hung, Leon Jay Williams, He Jiong, Abby Feng and Bosco Wong.
 The film is an unofficial sequel of the 2001 South Korean film "My Sassy Girl".
 It was released on November 5, 2010.
Day of the Dead 2: Contagium is a 2005 horror film written by Ana Clavell and directed by Clavell and James Dudelson, starring Justin Ipock, Laurie Maria Baranyay and John F. Henry III.
 It is an unofficial sequel to "1985's Day of the Dead".
 The film was released direct-to-video on  18, 2005 (2005--) in the United States.
Day of the Dead is a 1985 American horror film written and directed by George A. Romero and the third film in Romero's "Dead" series, being preceded by "Night of the Living Dead" (1968) and "Dawn of the Dead" (1978).
Il Successo (also known as "The Success") is a 1963 Italian comedy film directed by Mauro Morassi.
 It is considered an unofficial sequel of Dino Risi's "Il Sorpasso", with Vittorio Gassman and Jean-Louis Trintignant reprising their roles with slight changes.
 The same Risi directed part of the film.
Evil Dead II (also known in publicity materials as Evil Dead 2: Dead by Dawn) is a 1987 American horror comedy film directed by Sam Raimi and a parody sequel to the 1981 horror film "The Evil Dead".
 The film was written by Raimi and Scott Spiegel, produced by Robert Tapert, and stars Bruce Campbell as Ash Williams.
The Dead 2: India is a zombie horror film released in 2013.
 It is a sequel to, and follows up on the events of "The Dead" (2010).
 "The Dead 2: India" was produced by Road Trip Pictures in association with Latitude Films, directed by the Ford brothers, and stars Joseph Millson, Meenu Mishra, and Anand Krishna Goyal.
 In this movie, the action is set in the Indian states of Rajasthan and Maharashtra.
 "The Dead 2: India" had its world premiere at Film 4 FrightFest, held at London's Empire Leicester Square, on 22 August 2013, and was the opening film at Film 4 FrightFest.

Question: Day of the Dead 2: Contagium is an unofficial sequel to a film directed by who?
Answer: George A. Romero