[Carte Pneumatique: 1924 April 7, Paris: Konstantin Dmitrievich Balʹmont and Sergey Prokofiev to D[agmar] Chahovskoy]
MLA
Balʹmont, Konstantin Dmitrievich, 1867-1942. [Carte Pneumatique: 1924 April 7, Paris: Konstantin Dmitrievich Balʹmont and Sergey Prokofiev to D[agmar] Chahovskoy]. Box 4. 1924 April 7. https://collections.library.yale.edu/catalog/10082167.
APA, 6th edition
Balʹmont, Konstantin Dmitrievich, 1867-1942. (["Box 4"])(1924 April 7)[[Carte Pneumatique: 1924 April 7, Paris: Konstantin Dmitrievich Balʹmont and Sergey Prokofiev to D[agmar] Chahovskoy]]. https://collections.library.yale.edu/catalog/10082167.