Question: The American writer credited with more than thirty children's books wrote the third installment of what?
Context: Messenger is a 2004 young adult fiction by author Lois Lowry.  It forms the third installment of "The Giver Quartet" begun by her 1993 Newbery Medal-winning novel "The Giver".  This novel takes place about eight years after the events of "The Giver", and about six years after the events of "Gathering Blue".  Characters from the two earlier books reappear in "Messenger," connecting the novels more strongly.  Set in an isolated community known simply as Village, this novel focuses upon a boy named Matty, who serves as message-bearer through the ominous Forest that surrounds the community. Lois Lowry (born Lois Ann Hammersberg; March 20, 1937) is an American writer credited with more than thirty children's books.  She has won two Newbery Medals, for "Number the Stars" in 1990 and "The Giver" in 1994.  For her contribution as a children's writer, she was a finalist in 2000 and U.S. nominee again in 2004, as well as a finalist in 2016 for the biennial, international Hans Christian Andersen Award, the highest recognition available to creators of children's books.  Her book "Gooney Bird Greene" won the 2002 Rhode Island Children's Book Award. Dorothy Pulis Lathrop (April 16, 1891 – December 30, 1980) was an American writer and illustrator of children's books.  She was born in Albany, New York.  During a prolific career spanning from 1919 to 1967, she used her artistic skills as an illustrator of other authors’ children's fictional literature: more than 38 books were published with her illustrations.  Lathrop wrote and illustrated nine children's books and several topical nonfiction books.  She was also an accomplished printmaker.  Much of her work was devoted to the beauty and importance of animals. Peter Spier (June 6, 1927 – April 27, 2017) was a Dutch-born American illustrator and writer who created more than thirty children's books. Thomas Tidholm (born in Örebro on 11 April 1943) is a Swedish children's writer, poet, playwright, photographer, translator, and musician.  Since his debut as a poet in 1963, he has written poetry, novels, stage plays, and some thirty children's books (often collaborating with his wife, artist and writer Anna-Clara Tidholm).  He has directed short films for Sveriges Television, done youth theater for Unga Riks, and was a member of Swedish band Pärson Sound/International Harvester in the late sixties.  He's also known for the Swedish translation of the radio series and the first four novels in the The Hitchhiker's Guide series. Jane Kurtz (born April 17, 1952) is an American writer of including more than thirty picture books, middle-grade novels, nonfiction, ready-to-reads, and books for educators.  A member of the faculty of the Vermont College of Fine Arts MFA in children's and adult literature, Kurtz is an international advocate for literacy and writing.  She was also part of a small group of volunteers who organized the not-for-profit organization, Ethiopia Reads, which has established more than seventy libraries for children, published books, and built four schools in rural Ethiopia. The Third Gate is the fifth solo novel by American writer Lincoln Child.  The novel was released on June 12, 2012 by Doubleday.  The book is also the third installment in the Jeremy Logan series. Gonzo Papers, Vol.  3: Songs of the Doomed: More Notes on the Death of the American Dream is a book by the American writer and journalist Hunter S. Thompson, originally published in 1990.  This third installment of "The Gonzo Papers" is a chronologically arranged selection of stories, letters, journals and reporting, allowing readers to see how Thompson's brand of "new journalism," also termed Gonzo journalism, has evolved over the years.  It is a collection of Dr. Thompson's essays and articles.  This collection is mostly made up of pieces from the Reagan era, but there are also some older stories, including excerpts from his unfinished first novel, "Prince Jellyfish", which is still unpublished, and "The Rum Diary", which was not published on its own until 1998. The Amber House Trilogy is a series of young adult books by American author Kelly Moore and her daughters Tucker Reed and Larkin Reed.  The first book in the series, "Amber House", was published on October 1, 2012 through Arthur A. Levine Books. " Amber House" has been licensed in South America and Europe.  It was a featured title in the 2012 Scholastic Book Fair.  Its sequel, "Neverwas", was released on January 7, 2014.  Official publication dates for a third installment in the series, "Ever Shall", and a fourth and final installment, "Otherwhen", have not been announced as of early 2017. Out of Time’s Abyss is a fantasy-science fiction novel by American writer Edgar Rice Burroughs, the third of his Caspak trilogy.  The sequence was first published in "Blue Book Magazine" as a three-part serial in the issues for September, October and November 1918, with "Out of Time's Abyss" forming the third installment.  The complete trilogy was later combined for publication in book form under the title of "The Land That Time Forgot" (the title of the first part) by A. C. McClurg in June 1924.  Beginning with the Ace Books editions of the 1960s, the three segments have usually been issued as separate short novels.
Answer: The Giver Quartet