Affected by the news of the death of his daughter's friend, the dancer Wera Ouckama Knoop (1900–1919), Rilke set to work on Sonnets to Orpheus.[1]:p.481 The Sonnets frequently refer to Wera, both directly where he addresses her by name and indirectly in allusions to a "dancer" or the mythical Eurydice. Rilke wrote to the young girl's mother stating that Wera's ghost was "commanding and impelling" him to write.[13][14] In a rush of inspiration, Rilke worked on the Sonnets and renewed his focus towards completing the remainder of Duino Elegies. In one week, Rilke completed the unfinished elegies, and from 2 to 23 February 1922 he completed all the 55 sonnets of the two parts of Sonnets to Orpheus.[15] Rilke considered both collections to be "of the same birth".[15][16] In a letter to Klossowska on 9 February 1922, Rilke wrote: "what weighed me down and caused my anguish most is done ...