Papers include Kagan's correspondence, photographs, printed materials and audio tapes. All letters in the collection date from 1938-39, when he had moved his Petropolis operations to Brussels; there are items by Vladislav Khodasevich, Vladimir Nabokov, and Mikhail Osorgin, and others. Among the photographs are pictures of Ivan Bunin, Konstantin Fedin, and Evgeniĭ Zami︠a︡tin. Printed materials consist chiefly of books published by his firms; some of the books are inscribed, for example by Nikolaĭ Berdi︠a︡ev and Lev Karsavin. Included is a lengthy taped interview of Kagan by Marc Raeff in which Kagan discuses his life and publishing activities.

The papers consist of correspondence, manuscripts, notes, documents, photographs, subject files, and printed materials. Among the correspondents are Louis Marin, Mikhail Osorgin, Alekseĭ Remizov, Boris Ubegaun, George Vernadsky, and the "Eurasianists" Petr Savitskiĭ and Petr Suvchinskiĭ; there is one letter from Nikolaĭ Marr. There is the manuscript of Nikitin's memoirs, "Arabeski: pochemu i︠a︡ stal vostochnikom?" There are extensive notes of lectures by Nikolaĭ Berdi︠a︡ev in 1925. Numerous photographs date from Nikitin's service in Iran. Subject files concern the Eurasian movement (evraziĭstvo), and the Committee "For Return to the Homeland" ("Za Vozvrashchenie na Rodinu"). Printed materials largely consist of Nikitin's own writings.

Correspondence, manuscripts, documents, photographs, subject files, and printed materials of members of the Zernov family, especially Nikolaĭ M. Zernov. Correspondence includes letters from Nikolaĭ Berdi︠a︡ev, Archimandrite Kiprian, Alekseĭ Remizov, Vasiliĭ Zenḱovskiĭ, and copies of many letters from Gustave Kullmann to his wife Marii︠a︡, nʹee Zernova. Manuscripts include: memoirs by Sofii︠a︡ A. Zernova about her childhood, youth, and family; Sofii︠a︡ M. Zernova's albums, poems, diaries and memoirs about the Civil War and the emigration in Europe; manuscripts by Nikolaĭ Zernov on religious and literary themes; a report by a Lt. Shokotov on his White Army detached service in 1917-1919; a brief manuscript by Vladimir M. Zernov claiming that syphillis was a contributing factor in Lenin's death; and manuscripts and speeches by Kullmann. Subject files include biographical information collected by Nikolaĭ Zernov on many emigre Orthodox churchmen and religious writers, and materials relating to Kullmann and the Zernov family.