Question: Who wrote the books  the fantasy series Sophie Turner stars in was based on?

full_context: Document 1: Emma Watson: Emma Charlotte Duerre Watson (born 15 April 1990) is a British actress, model, and activist. Born in Paris and brought up in Oxfordshire, Watson attended the Dragon School and trained as an actress at the Oxford branch of Stagecoach Theatre Arts. She rose to prominence after landing her first professional acting role as Hermione Granger in the "Harry Potter" film series, having acted only in school plays previously. Watson appeared in all eight "Harry Potter" films from 2001 to 2011, earning worldwide fame, critical accolades, and around $60 million.
Document 2: Maisie Williams: Margaret Constance "Maisie" Williams (born 15 April 1997) is an English actress. She made her professional acting debut as Arya Stark in the HBO fantasy television series "Game of Thrones" in 2011, for which she won the EWwy Award for Best Supporting Actress in a Drama, the Portal Award for Best Supporting Actress – Television and Best Young Actor, and the Saturn Award for Best Performance by a Younger Actor. In 2016, she was nominated for a Primetime Emmy Award for Outstanding Supporting Actress in a Drama Series.
Document 3: Catelyn Stark: Catelyn Stark (née Tully) is a fictional character in the "A Song of Ice and Fire" series of fantasy novels by American author George R. R. Martin, and its television adaptation "Game of Thrones". She is a prominent point of view character in the novels.
Document 4: Sansa Stark: Sansa Stark is a fictional character created by American author George R. R. Martin. She is a prominent character in Martin's award-winning "A Song of Ice and Fire" series.
Document 5: Sophie Turner Laing: Sophie Turner Laing (born 7 September 1969) is a British businesswoman and media executive. She has been Chief Executive Officer of global content creator, producer and distributor Endemol Shine Group since December 2014. Prior to taking up her current role, she held a number of senior positions at Sky in the UK, including Director of Movies and Managing Director of Content. She had previously worked for the BBC as Acting Director of Television and, along with Peter Orton, was a founder of HiT Entertainment.
Document 6: Gwendoline Christie: Gwendoline Christie (born 28 October 1978) is an English actress and model.
Document 7: Hannah Murray: Hannah Murray (born 1 July 1989) is an English actress best known for portraying Cassie Ainsworth in the E4 teen drama series "Skins" (2007–2008; 2013), for which she was the recipient of a BAFTA Audience Award and Gilly in the HBO series "Game of Thrones" (2012–present), for which she has been nominated for two Screen Actors Guild Awards. She has received praise for her performances in the Off West End play "Martine" (2014) and the film "Bridgend".
Document 8: Jaime Lannister: Jaime Lannister is a fictional character in the "A Song of Ice and Fire" series of fantasy novels by American author George R. R. Martin, and its television adaptation "Game of Thrones". He becomes a prominent point of view character in the novels beginning in "A Storm of Swords" (2000).
Document 9: Bran Stark: Brandon Stark, typically called Bran, is a fictional character in the "A Song of Ice and Fire" series of fantasy novels by American author George R. R. Martin, and its television adaptation "Game of Thrones". Martin told "Rolling Stone" in 2014 that Bran's chapter with Jaime and Cersei Lannister is what "hooked" many readers early in the first novel.
Document 10: Daenerys Targaryen: Daenerys Targaryen is a fictional character in George R. R. Martin's "A Song of Ice and Fire" series of novels, as well as the television adaptation, "Game of Thrones", where she is portrayed by Emilia Clarke. In the novels, she is a prominent point of view character. She is one of the most popular characters in the series, and "The New York Times" cites her as one of the author's finest creations.
Document 11: Sophie Turner: Sophie Turner (born 21 February 1996) is an English actress. Turner made her professional acting debut as Sansa Stark on the HBO fantasy television series "Game of Thrones" (2011–present), which brought her international recognition.
Document 12: Sophie Turner (model): Sophie Turner (born 30 April 1984) is an Australian model, reality television personality and lawyer who first came to prominence as a contestant on the Australian television series "Search for a Supermodel".
Document 13: Cersei Lannister: Cersei Lannister is a fictional character in the "A Song of Ice and Fire" series of fantasy novels by American author George R. R. Martin, and its television adaptation "Game of Thrones", where she is portrayed by Lena Headey. In the novels, she is a point of view character.
Document 14: Brienne of Tarth: Brienne of Tarth is a fictional character in George R. R. Martin's "A Song of Ice and Fire" series of fantasy novels. She is a prominent point of view character in the fourth novel, "A Feast for Crows", and a main character in the television adaptation. She is introduced in the second novel in the series, "A Clash of Kings".
Document 15: Jon Snow (character): Jon Snow is a fictional character in the "A Song of Ice and Fire" series of fantasy novels by American author George R. R. Martin, and its television adaptation "Game of Thrones". He is a prominent point of view character in the novels, and has been called one of the author's "finest creations" and most popular characters by "The New York Times". Jon is a main character in the TV series, and his storyline in the 2015 season 5 finale generated a strong reaction among viewers. Speculation about the character's parentage has also been a popular topic of discussion among fans of both the books and the TV series.
ground_truth: George R. R. Martin