The paper contains three letters written by Vallée Poussin to Luzin dated 4 February 1933, 8 March 1933 and 21 March 1933. Vallée Poussin comments in these letters on the fact, which is of great interest to him, that Luzin used slightly different classifications of the same sets as he had studied.
Ang papel ay naglalaman ng tatlong titik na isinulat ng Vallee Poussin sa Luzin petsang 4 Pebrero 1933, 8 Mar 1933 at 21 March 1933. Vallee Poussin comments sa mga sulat na ito sa katunayan, kung saan ay apo ng interes sa kanya, na bahagyang Luzin ginagamit ng iba't ibang klasipikasyon ng parehong set bilang niya-aral.