The poems that form this collection were written between 1936-39. A selection from them had been published in 1957 under the title "Volverse sombra y otras poemas". In the first edition of his "Poesías completas" that his daughter Solita brought out in 1971, she restored the original title and gathered together 21 poems. In the 1981 edition, she added a further 26 poems, considerably expanding the size of the collection. The manuscript, which existed almost entirely in typescript, was made up of 5 distinct groups of texts, 3 found in Gilman Hall at the Johns Hopkins campus and the other 2 amongst the poet's papers in his house in Newland Road, Baltimore. The state of the manuscripts varied between finished and properly typed up, finished by the poet but not properly typed up, and draft. Amongst the drafts, there were some that the editor felt were complete enough to merit publication.