Question: In what year was the follow up to "The Purple Prince of Oz released?

full_context: Document 1: The Silver Princess in Oz: The Silver Princess in Oz (1938) is the thirty-second of the Oz books created by L. Frank Baum and his successors, and the eighteenth written by Ruth Plumly Thompson. It was illustrated by John R. Neill.
Document 2: List of Uncle Remus characters: This is a list of fictional characters in the book The Complete Tales of Uncle Remus. Uncle Remus himself, and a couple boys to whom he tells the tales, appear as framing devices & narrators in all the stories. The stories of Uncle Remus' visitor Daddy Jack often also include unnamed stock roles such as a daughter, a foolish bird, a man, a mother, a snake, a wise bird, and a witch.
Document 3: List of Oz books: 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.
Document 4: Pirates in Oz: Pirates in Oz (1931) is the twenty-fifth in the series of Oz books created by L. Frank Baum and his successors, and the eleventh written by Ruth Plumly Thompson. It was illustrated by John R. Neill.
Document 5: Wish Way: A Wish Way is a device that appears in three of the Oz books of Ruth Plumly Thompson, "The Royal Book of Oz", "The Hungry Tiger of Oz", and "The Lost King of Oz". Two Wish Ways are found in distinctly different locations, both in the Winkie Country.
Document 6: List of Oz characters: This is a list of characters in the original sequel Oz books by American author L. Frank Baum, and in the later continued Oz series by his grandson Roger S. Baum, Ruth Plumly Thompson, John R. Neill, Jack Snow, Rachel Cosgrove Payes, Eloise Jarvis McGraw and Lauren McGraw, Dick Martin, Eric Shanower, and Sherwood Smith. Characters from Gregory Maguire's "Wicked" are not included, as his works, among others such as the work of March Laumer, are considered "heretical" in Baum scholarship (The term "heretical" was first applied to these books by Dr. Stephen J. Teller of Pittsburg State University in the Winter 1988 issue of "The Baum Bugle" and appears regularly in Oz fandom).
Document 7: The Lost King of Oz: The Lost King of Oz (1925) is the nineteenth in the series of Oz books created by L. Frank Baum and his successors, and the fifth written by Ruth Plumly Thompson. It was Illustrated by John R. Neill.
Document 8: List of published Oz apocrypha: This page is a supplement to List of Oz books featuring published books, often by small publishing houses. Their canonicity is up to the individual reader, with some purists considering them apocryphal. As the Baum Oz books are in the public domain, no clearance needs to be obtained to write and publish fiction about the Oz characters, professionally or otherwise, making the question of canonicity somewhat subjective. Additionally, both of Jack Snow's Oz books are in the public domain in the United States, as are Ruth Plumly Thompson's "The Royal Book of Oz", "Kabumpo in Oz", "The Wishing Horse of Oz", "Captain Salt in Oz", "Handy Mandy in Oz", "The Silver Princess in Oz", and "Ozoplaning with the Wizard of Oz", making the distinctive elements in those books usable as public domain content. The most dramatic changes in her books are in "The Lost King of Oz" and "The Giant Horse of Oz", both of which remain protected under U.S. copyright law, and has rendered some known manuscripts unpublishable. The Oz books of John R. Neill, Rachel R. Cosgrove, and Eloise Jarvis McGraw and her daughter Lauren are all protected under U.S. copyright, making their characters and developments unusable by others without permission.
Document 9: Yankee in Oz: Yankee in Oz is a 1972 Oz novel by Ruth Plumly Thompson. It was the first published by The International Wizard of Oz Club. A letter from the Henry Regnery Company, which bought Reilly & Lee, is reproduced in the front indicating the publisher's blessing for the new Oz book to appear. It was originally written in 1959, but because the Oz books were not selling, it was not published. The first two editions of the book were published in 8½ x 11 inch format and running only 94 pages. This was done at the request of illustrator Dick Martin to reduce the number of required illustrations and to show them closer to the actual size they were drawn. The second printing (1986) featured a new cover, with the first edition artwork reprinted preceding the title page. The third printing (2007) is standard Oz book size. Its cover is a gaudier redesign of the second edition cover. The book also features maps by James E. Haff, and as such, Thompson correctly places the Winkie Country in the west of Oz.
Document 10: The Purple Prince of Oz: The Purple Prince of Oz (1932) is the 26th in the series of Oz books created by L. Frank Baum and his successors, and the 12th written by Ruth Plumly Thompson. It was illustrated by John R. Neill.
Document 11: Peter Brown (Oz): Peter Brown is a major character in the Oz novels of Ruth Plumly Thompson, who continued the series of Oz books after the death of their creator, L. Frank Baum. Thompson used Peter as the protagonist in three of her books: "The Gnome King of Oz" (1927), "Jack Pumpkinhead of Oz" (1929), and "Pirates in Oz" (1931).
Document 12: The Royal Book of 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.
Document 13: Jinnicky the Red Jinn: The Red Jinn, later known as Jinnicky, is one of Ruth Plumly Thompson's most frequently occurring characters in her Oz books. He was first introduced in "Jack Pumpkinhead of Oz" as a mysterious figure who educates Jack Pumpkinhead on the use of the Pirate Sack. Although a detailed description is included in the text, "Jack Pumpkinhead of Oz" includes no illustrations of the Red Jinn aside from a gruesome color plate that did not appear outside the first edition, in which he has massive piercings. He was reintroduced, drawn, and given the name Jinnicky in "The Purple Prince of Oz"; he also appeared in the follow-up, "The Silver Princess in Oz". (He makes a cameo appearance in "The Wishing Horse of Oz", and he is the principal pre-existing character in Thompson's sub-canonical penultimate Oz book, "Yankee in Oz"). Jack Snow apparently thought the Red Jinn was a separate character, for he considered "The Purple Prince of Oz" Jinnicky's first appearance in "Who's Who in Oz", though he did not include a separate Red Jinn entry.
Document 14: Tin Woodman: The Tin Woodman, better known as either the Tin Man or (incorrectly) the Tin Woodsman (the third name appears only in adaptations, the first—and in rare instances, the second—was used by Baum), is a character in the fictional Land of Oz created by American author L. Frank Baum. Baum's Tin Woodman first appeared in his classic 1900 book "The Wonderful Wizard of Oz", and reappeared in many other Oz books. In late 19th-century America, men made out of various tin pieces were used in advertising and political cartoons. Baum, who was editing a magazine on decorating shop windows when he wrote "The Wonderful Wizard of Oz", was reportedly inspired to invent the Tin Woodman by a figure he had built out of metal parts for a shop display.
Document 15: The Wishing Horse of Oz: The Wishing Horse of Oz (1935) is the twenty-ninth in the series of Oz books created by L. Frank Baum and his successors, and the fifteenth written by Ruth Plumly Thompson. It was Illustrated by John R. Neill. This book marked the point at which Thompson had written more Oz books than Baum himself.
ground_truth: 1938