Question: Who published the prequel to Sphereland?

Context articles: The Affair (Child novel)
Sphereland
Dune prequel series
The Sin Eater’s Daughter
PhD: Phantasy Degree
Flatland
List of Tail of the Moon chapters
Transformers: Movie Prequel
Dead to Rights II
Enemy Territory: Quake Wars

The Affair is the sixteenth book in the Jack Reacher series written by Lee Child but is a prequel set chronologically before most of them.
 It was published on 29 September 2011 in the United Kingdom and was published on 27 September 2011 in the USA.
 "The Affair" is a prequel set six months before Child's first novel, "Killing Floor" and setting out the explosive circumstances under which Reacher's career in the United States Army was terminated.
 This book is written in the first person.
Sphereland: A Fantasy About Curved Spaces and an Expanding Universe is a 1965 novel by Dionys Burger, and is a sequel to "Flatland", a novel by "A Square" (a pen name of Edwin Abbott Abbott).
 The novel expands upon the social and mathematical foundations on which "Flatland" is based.
 It is markedly different from the first novel in that it has a more prosaic ending and treatment of society.
The "Dune" prequel series is a sequence of novel trilogies written by Brian Herbert and Kevin J. Anderson.
 Set in the "Dune" universe created by Frank Herbert, the novels take place in various time periods before and in between Herbert's original six novels, which began with 1965's "Dune".
 In 1997, Bantam Books made a $3 million deal with the authors for three "Dune" prequel novels, partially based upon notes left behind by Frank Herbert, that would come to be known as the "Prelude to Dune" trilogy.
 Starting with 1999's "", the duo have published ten "Dune" prequel novels to date.
 In 2011 "Publishers Weekly" called the series "a sprawling edifice that Frank Herbert’s son and Anderson have built on the foundation of the original "Dune" novels."
The Sin Eater's Daughter is a young adult fantasy series written by Melinda Salisbury and published by Scholastic Press.
 The first book in the series, "The Sin Eater’s Daughter", was published on 24 February 2015 and marked Salisbury's first book in print.
 The second book in the series, "The Sleeping Prince", was published the following year along with a short story prequel, "The King of Rats".
 The third book in the series, "The Scarecrow Queen", was released in 2017.
 A fourth book, "The Heart Collector", was also published in 2017, it is a collection of 3 short stories from the same fictional universe, including the previously released "The King of Rats", as well as 2 new stories, "The Heart Collector" and "Mully No-Hands".
PhD: Phantasy Degree (Korean: 마스터스쿨 올림프스 "Maseuteo Seukur Ollimpeuseu", lit.
 "Master School Olympus") , is a manhwa series created by Son Hee-joon.
 The series is published by in English by Tokyopop.
 There are currently 10 volumes published, and the series' original publisher, Daiwon C.I. lists it as ongoing, but no new volumes have been published since 2005.
 A one-volume prequel to the series entitled "Magic Academy Zeus" (매직 아카데미 제우스, "Maejig Akademi Jeusu") was published in South Korea in 1998.
Flatland: A Romance of Many Dimensions is a satirical novella by the English schoolmaster Edwin Abbott Abbott, first published in 1884 by Seeley & Co. of London.
Written and illustrated by Rinko Ueda, Tail of the Moon Prequel: The Other Hanzo(u) (月の吐息 愛の傷 , Tsuki no Toiki no Ai no Kizu ) was originally published as a oneshot in "Margaret" magazine in 2001, but was soon followed by another oneshot, Tsuki no Toiki Natsu no Yume (月の吐息 夏の夢 ) in 2002, and then the series, Tail of the Moon.
 The "Tail of the Moon" manga was serialized in "Margaret" from 2002 until its completion in 2007.
 Both the prequel and the series are licensed by Viz Media in North America for an English language release as part of their Shojo Beat line of manga.
 Viz also previewed the series in their now-defunct "Shojo Beat" magazine.
 The series is also licensed for release in Taiwan by Sharp Point Press.
 Beginning in October 2010, the series is being re-released as bunko editions in Japan.
Transformers: Movie Prequel, published by IDW Publishing, is a 2007 comic book limited series that serves as a prequel to the 2007 film "Transformers".
 It is written by Simon Furman and IDW editor-in-chief Chris Ryall, who was allowed to read the film's script, and penciled by artist Don Figueroa.
 , a 4 issue adaptation of the film itself, was released weekly throughout the month of June in the run up to the film's release.
Dead to Rights II is a third-person action video game, developed by Widescreen Games, published by Namco, and released in 2005.
 Serving as a prequel to "Dead to Rights", it begins with the story of Jack Slate and Shadow before the events of the original game.
 A PSP prequel, "", released on June 28, 2005.
Enemy Territory: Quake Wars is a first-person shooter video game developed by Splash Damage and published by Activision for Microsoft Windows, Linux, Mac OS X, PlayStation 3 and Xbox 360.
 The prequel to "Quake II", "Quake Wars" is set in the same science fiction universe as "Quake II" and "Quake 4", with a minimal back-story serving as a prequel to "Quake II".
 It is the second multiplayer-focused game in the "Quake" series after "Quake III Arena".