Which literary piece by Geoffrey Chaucer serves as an elegy dedicated to Blanche of Lancaster?

Explanation

Among Chaucer's works, 'The Book of the Duchess' is recognized as an elegy composed in memory of Blanche of Lancaster. The other titles, such as 'The House of Fame,' 'Troilus and Criseyde,' and 'The Legend of Good Women,' do not serve this commemorative purpose.