Question: The 1985 film "Return to Oz" is loosely based on which of L. Frank Baum's books?

Context articles: The Dreamer of Oz: The L. Frank Baum Story
Return to Oz
Roger S. Baum
L. Frank Baum's Juvenile Speaker
List of Oz books
The Marvelous Land of Oz
The Royal Book of Oz
Plays of L. Frank Baum
The Wizard of Oz (1933 film)
Journey Back to Oz

The Dreamer of Oz: The L. Frank Baum Story is a 1990 made-for-television biographical film starring John Ritter as Lyman Frank Baum, the man who wrote "The Wonderful Wizard of Oz" and thirteen of the other Oz books.
 Also starring in this TV movie was Annette O'Toole as Baum's supportive wife, Maud, and Rue McClanahan as Baum's tough mother-in-law, Matilda Gage.
 John's son, Jason Ritter, makes his debut in this telefilm as Harry Neal Baum.
 At the time of the film's debut, O'Toole and Ritter also starred in "It", a TV miniseries where they played a couple.
Return to Oz is a 1985 fantasy adventure film directed and written by Walter Murch, an editor and sound designer, co-written by Gill Dennis and produced by Paul Maslansky.
 It stars Nicol Williamson as the Nome King, Jean Marsh as Princess Mombi, Piper Laurie as Aunt Em, Matt Clark as Uncle Henry and introduces Fairuza Balk as Dorothy Gale.
 It is loosely based on L. Frank Baum's "Oz" novels, mainly "The Marvelous Land of Oz" (1904) and "Ozma of Oz" (1907), yet is set six months after the events of the first novel, "The Wonderful Wizard of Oz" (1900) took place.
 Although it is not a sequel and unrelated to the 1939 Metro-Goldwyn-Mayer film, "The Wizard of Oz", it borrows a few elements of it such as the ruby slippers.
Roger Stanton Baum (born 1938) is a former banker and stockbroker, and currently (as of 2005) a children's author, residing in Las Vegas.
 Baum publishes under the name Roger S. Baum.
 Baum is a former resident of Los Angeles.
 He also tours the country, reading from and signing his children's books.
 Baum is a great-grandson of L. Frank Baum, the original creator of the "Oz" series, and grandson of Frank Joslyn Baum, who published "The Laughing Dragon of Oz" in 1935.
 Many of Roger S. Baum's children's books are set in the same world.
L. Frank Baum's Juvenile Speaker: Readings and Recitations in Prose and Verse, Humorous and Otherwise is an anthology of literary works by L. Frank Baum, author of the Oz books.
 The book was first published in 1910, with illustrations by veteran Baum artists John R. Neill and Maginel Wright Enright; a subsequent 1912 edition was retitled Baum's Own Book for Children.
 The book constitutes a complex element in the Baum bibliography.
The Oz books form a book series that begins with "The Wonderful Wizard of Oz" (1900) and relate the fictional history of the Land of Oz.
 Oz was created by author L. Frank Baum, who went on to write fourteen full-length Oz books.
 All of the Baum written books are in the public domain in the United States.
 Even while he was alive, Baum was styled as "the Royal Historian of Oz" to emphasize the concept that Oz is an actual place.
 The illusion created was that characters such as Dorothy and Princess Ozma related their adventures in Oz to Baum themselves, by means of wireless telegraph.
The Marvelous Land of Oz: Being an Account of the Further Adventures of the Scarecrow and the Tin Woodman, commonly shortened to The Land of Oz, published on July 5, 1904 , is the second of L. Frank Baum's books set in the Land of Oz, and the sequel to "The Wonderful Wizard of Oz" (1900).
 This and the next 34 Oz books of the famous 40 were illustrated by John R. Neill.
 The book was made into an episode of "The Shirley Temple Show" in 1960, and into a Canada/Japan co-produced animated series of the same name in 1986.
 It was also adapted in comic book form by Marvel Comics, with the first issue being released in November 2009.
 Plot elements from "The Marvelous Land of Oz" are included in the 1985 Disney feature film "Return to Oz".
The Royal Book of Oz (1921) is the fifteenth in the series of Oz books, and the first by Ruth Plumly Thompson, to be written after L. Frank Baum's death.
 Although Baum was credited as the author, it was written entirely by Thompson.
 Beginning in the 1980s, some editions have correctly credited Thompson, although the cover of the 2001 edition by Dover Publications credits only Baum.
 The original introduction claimed that the book was based on notes by Baum, but this has been disproved.
 Baum's surviving notes, known as "An Oz Book" are known from four typewritten pages found at his publisher's, but their authenticity as Baum's work has been disputed.
 Even if genuine, they bear no resemblance to Thompson's book.
The plays of L. Frank Baum are an important aspect of Baum's writing career about which some of the least is known.
 While even most brief biographies, long before the Internet, have noted Baum's work as a playwright, these works have been rarely performed beyond his lifetime, and almost none have been published aside from two scenarios and a first act of three unfinished works in "The Musical Fantasies of L. Frank Baum", compiled with an introduction by Alla T. Ford.
 Aside from his youthful success with "The Maid of Arran", his blockbuster eight-year run with "The Wizard of Oz", his failure with "The Woggle-Bug", and "The Tik-Tok Man of Oz" as source material for his novel, "Tik-Tok of Oz", very little is known about his dramatic output, and mostly from the publications of Michael Patrick Hearn, Susan Ferrara, and Katharine M. Rogers.
 Hearn identifies 41 different titles in the bibliography of the 2000 edition of "The Annotated Wizard of Oz", plus one play without a title, although some of these titles clearly refer to drafts of the same play, such as the early titles of "The Tik-Tok Man of Oz".
The Wizard of Oz (1933) is a Canadian animated short film directed by Ted Eshbaugh.
 The story is credited to "Col. Frank Baum."
 Frank Joslyn Baum, a Lieutenant Colonel in the United States Army and eldest son of writer L. Frank Baum, was involved in the film's production, and may have had an involvement in the film's script, which is loosely inspired by the elder Baum's novel, "The Wonderful Wizard of Oz".
 It runs approximately eight and a half minutes and is nearly absent of language, working mainly with arrangements of classical music created by Carl W. Stalling.
Journey Back To Oz is a 1972 American animated fantasy-adventure film and an official sequel to the 1939 Metro-Goldwyn-Mayer film "The Wizard of Oz" produced by Filmation.
 It is loosely based on L. Frank Baum's second Oz novel, "The Marvelous Land of Oz", although Baum received no screen credit.
 However, the Wizard was nowhere to be found, at least in the theatrical version of the film.
 A television version shown in 1976 on ABC featured live-action segments starring Bill Cosby as the Wizard.