From a book trader in Canada I bought a letter from Joan Miro which he has written to his publisher Georges Hugnet “Varengeville s/ mer, 25.3.1940” –
It is an excellent letter from the time in Varengeville (Miro stayed there from 1938 until latest july 1940 and went to Palma due to german invasion in France).
In his biography (http://miro.palmademallorca.es/obra_grafica/biograf1_ENG_REV.html) you can read ” Miró began his famous Constellations series of twenty-three paintings that have a printwork parallel in L’usage de la parole, a print made in April, 1940 for a poetry magazine founded by Georges Hugnet, in which Miró played with cutout plates, creating a dialog between presence and absence, between inked and white areas, a process he repeated in many series thereafter.”
I am very sure that this letter is exactly describing the circumstances concerning the production of those prints: Miro mentions, that he received the copper plates and started to engrave. He mentions „Zervos“ and „Lacourière“ where he hopes to be working soon.