Question: The Sarantine Mosaicv alludes to works by which poet who helped to found the Abbey Theater?

full_context: Document 1: The Darkest Road: The Darkest Road is the third novel of The Fionavar Tapestry trilogy by Guy Gavriel Kay. "The Summer Tree" and "The Wandering Fire" are the first two books.
Document 2: John Butler Yeats: John Butler Yeats (16 March 1839 – 3 February 1922) was an Irish artist and the father of William Butler Yeats, Lily Yeats, Elizabeth Corbett "Lolly" Yeats and Jack B. Yeats. He is probably best known for his portrait of the young William Butler Yeats which is one of a number of his portraits of Irishmen and women in the Yeats museum in the National Gallery of Ireland. His portrait of John O'Leary (1904) is considered his masterpiece (Raymond Keaveney 2002).
Document 3: Guy Gavriel Kay: Guy Gavriel Kay {'1': ", '2': ", '3': ", '4': "} (born November 7, 1954) is a Canadian writer of fantasy fiction. Many of his novels are set in fictional realms that resemble real places during real historical periods, such as Constantinople during the reign of Justinian I or Spain during the time of El Cid. Those works are published and marketed as historical fantasy, although Kay has expressed a preference to avoid genre categorization.
Document 4: Anne Yeats: Anne Butler Yeats (9 May 1919 – 4 July 2001) was an Irish painter and stage designer. She was a daughter of the poet William Butler Yeats and a niece of the painter Jack B. Yeats, niece of Lily Yeats, an embroiderer associated with the Celtic Revival, and botanic artist Elizabeth Yeats. Her brother Michael Yeats was a politician.
Document 5: James Joyce: James Augustine Aloysius Joyce (2 February 1882 – 13 January 1941) was an Irish novelist, short story writer, and poet. He contributed to the modernist avant-garde and is regarded as one of the most influential and important authors of the 20th century. Joyce is best known for "Ulysses" (1922), a landmark work in which the episodes of Homer's "Odyssey" are paralleled in a variety of literary styles, perhaps most prominently stream of consciousness. Other well-known works are the short-story collection "Dubliners" (1914), and the novels "A Portrait of the Artist as a Young Man" (1916) and "Finnegans Wake" (1939). His other writings include three books of poetry, a play, his published letters and occasional journalism.
Document 6: Seamus Heaney: Seamus Justin Heaney, ( ; 13 April 1939 – 30 August 2013) was an Irish poet, playwright, translator and lecturer from Northern Ireland. He received the 1995 Nobel Prize in Literature.
Document 7: W. B. Yeats: William Butler Yeats ( ; 13 June 186528 January 1939) was an Irish poet and one of the foremost figures of 20th century literature. A pillar of both the Irish and British literary establishments, he helped to found the Abbey Theatre, and in his later years served as an Irish Senator for two terms. Yeats was a driving force behind the Irish Literary Revival along with Lady Gregory, Edward Martyn and others.
Document 8: LÉ William Butler Yeats (P63): LÉ "William Butler Yeats" (P63) is a "Samuel Beckett"-class offshore patrol vessel (OPV) named for poet W. B. Yeats, the ship is the third in a series of vessels designed by Vard Marine and built by Babcock Marine Appledore. The ship was floated out of the shipyard in March 2016, started trials in July 2016, and arrived at Haulbowline naval base in late July 2016. The ship was formally commissioned in a ceremony in Galway on 17 October 2016. During the ceremony it was officially named by a granddaughter of the poet, Caitriona Yeats.
Document 9: Under Heaven (novel): Under Heaven is the eleventh novel by Canadian fantasy author Guy Gavriel Kay. It was published in April 2010 by Viking Canada. Set in a fantasied Tang China, it is Kay's first work set outside of a fantasied European or Mediterranean setting. The novel is based on a fictionalized version of the An Shi Rebellion. "Under Heaven" takes place in a completely new world, as seen by it having only one moon as opposed to the two moons normally present in Guy Gavriel Kay's works. In 2013 he published a second novel, "River of Stars", set approximately 400 years later in the same world.
Document 10: George Bernard Shaw: George Bernard Shaw ( ; 26 July 1856 – 2 November 1950), known at his insistence simply as Bernard Shaw, was an Irish playwright, critic and polemicist whose influence on Western theatre, culture and politics extended from the 1880s to his death and beyond. He wrote more than sixty plays, including major works such as "Man and Superman" (1902), "Pygmalion" (1912)" and Saint Joan" (1923). With a range incorporating both contemporary satire and historical allegory, Shaw became the leading dramatist of his generation, and in 1925 was awarded the Nobel Prize in Literature.
Document 11: The Wandering Fire: The Wandering Fire is the second novel of The Fionavar Tapestry trilogy by Guy Gavriel Kay. "The Summer Tree" is the first.
Document 12: The Fionavar Tapestry: The Fionavar Tapestry is a trilogy of fantasy novels by Guy Gavriel Kay, first published between 1984 and 1986. The novels are partly set in our own contemporary world, but mostly in the fictional world of Fionavar. It is the story of five University of Toronto senior law and medical students, who are drawn into the 'first world of the Tapestry' by the mage Loren Silvercloak. Once there, each discovers his or her own role and destiny in the framework of an epic conflict. The books original cover illustrations were created by Martin Springett.
Document 13: River of Stars: River of Stars is the twelfth novel by Canadian fantasy author Guy Gavriel Kay. It was published in April 2013 by Roc Hardcover. It is Kay's second work set in an alternate history of China, taking place 400 years after his previous novel, "Under Heaven". The novel is a fictionalized account of the beginning of the Jin–Song Wars during the Song Dynasty.
Document 14: Ceremony of Innocence: Ceremony of Innocence is a Windows CD-ROM-based game released in 1997. It used a mystery narrative based on the "Griffin and Sabine" novel by Nick Bantock. The title was taken from the poem "The Second Coming" by Irish poet William Butler Yeats.
Document 15: The Sarantine Mosaic: The Sarantine Mosaic is a historical fantasy duology by Guy Gavriel Kay, comprising "Sailing to Sarantium" and "Lord of Emperors". The titles of the novels allude to works by poet W. B. Yeats.
ground_truth: William Butler Yeats