Question: Which book series from Rick Riordan do both the fantasy novel The Hidden Oracle and the Camp Half-Blood-Chronicles have in common?
Context: The Hidden Oracle is a fantasy novel based on Greek and Roman mythology written by Rick Riordan.  It was published on May 3, 2016, and is the first book in "The Trials of Apollo" series, the second spin-off of the "Percy Jackson & the Olympians" series.  The book and its cover art by John Rocco were first announced in 2015.  It has been published in hardcover, audiobook, ebook, and large-print editions.  To date, "The Hidden Oracle" has been translated into 19 languages from its original English. Camp Half-Blood Chronicles is a media franchise created by author Rick Riordan, encompassing three five-part novel series, three short-story collections, two myth anthology books, a stand-alone short story, an essay collection, a guide, four graphic novels, two films, a video game, a musical, and other media.  Set in the modern world, it focuses on groups of demi-god teenagers, and features many characters from Greek and Roman mythology.  The first series, "Percy Jackson & the Olympians", follows the adventures of a teen named Percy Jackson at a summer camp for Greek demigods.  The second series, "The Heroes of Olympus", introduces several more lead characters and a second camp for Roman demigods.  The third series, "The Trials of Apollo", follows the now-mortal god Apollo, with appearances by many characters from the first and second series. The Sword of Summer is the first novel in the "Magnus Chase and the Gods of Asgard" trilogy, written by American author Rick Riordan.  It is a fantasy novel based on Norse mythology.  It was released on October 6, 2015 by Disney•Hyperion, an imprint of Disney Book Group.  It is narrated in the first-person view by Magnus Chase, 16-year-old demigod and homeless orphan.  After his death and arrival in the Norse afterlife, Magnus discovers that he is the son of the Norse deity, Frey, and must stop Fenris Wolf from escaping his prison and ending the world. The Heroes of Olympus is a pentalogy of adventure, mythological fiction and fantasy novels by American author Rick Riordan that collectively form a sequel series to the "Percy Jackson & the Olympians" series.  This series details a conflict between Greek and Roman demigods and Gaea, the earth goddess.  Riordan introduces Roman mythology into his sequel series as well as several new characters.  The first book of the series, "The Lost Hero", was published on October 12, 2010.  The final entry in the series, "The Blood of Olympus", was published on October 7, 2014. The Son of Neptune is a 2011 fantasy novel, the second book in "The Heroes of Olympus" series written by Rick Riordan.  The story follows the adventures of amnesiac Percy Jackson, a demigod son of Poseidon the god of the sea, as he meets a camp of Roman demigods and goes to Alaska with his new friends Hazel Levesque and Frank Zhang to free the Greek god of death, Thanatos and help save the world from Gaea, the earth goddess. The Trials of Apollo is a series of fantasy adventure mythological fiction novels written by American author Rick Riordan that collectively form a sequel to the "Heroes of Olympus" series.  The first book in the series, "The Hidden Oracle", was released on May 3, 2016.  The second book in the series, "The Dark Prophecy", was released on May 2, 2017. The House of Hades is a 2013 fantasy novel based on Greek and Roman mythology written by Rick Riordan.  It is the fourth book in "The Heroes of Olympus" series, which succeeds the "Percy Jackson & the Olympians" series.  It is narrated in third person by the seven demigods of the "Prophecy of Seven".  The demigods are continuing on their quest from the end of "The Mark of Athena" to close the Doors of Death and slow the progress of the goddess Gaea's army in the mortal world. The Oracle, with the United States title The Oracle Betrayed, is a young adult fantasy novel by Catherine Fisher, first published in 2003.  "The Oracle" is the first of the "Oracle Prophecies Trilogy".  The others are The Archon (2004) and The Scarab (2005); with the US titles being The Sphere of Secrets and The Day of the Scarab, respectively.  The book was shortlisted for the 2003 Whitbread Awards. Perseus "Percy" Jackson is a fictional character, the title character and narrator of Rick Riordan's "Percy Jackson & the Olympians" series.  He is also one of seven main protagonists of the sequel series "The Heroes of Olympus", appearing in every book except "The Lost Hero," and appears in the ongoing "Trials of Apollo" series, making him one of the few characters to appear in all three series of the Camp Half-Blood chronicles.  He has also been a narrator and protagonist in Riordan's Greco-Roman/Egyptian crossover stories, part of the "Demigods and Magicians" collection.  The character serves as the narrator in "Percy Jackson's Greek Gods" and "Percy Jackson's Greek Heroes", also by Rick Riordan. Percy Jackson & the Olympians, often shortened to Percy Jackson, is a pentalogy of adventure and mythological fiction books written by American author Rick Riordan, and the first book series in the Camp Half-Blood Chronicles.  Five supplementary books, along with three graphic novels, have also been released.  More than 45 million copies of the books have been sold in more than 35 countries.
Answer: Percy Jackson & the Olympians