1. Académie des Sciences (cited as “ADS”): Comité secret, registres des séances. Register 1J25, “Conférence interalliée des Académies scientifiques”, is currently being reclassified. This bound volume contains a typescript of notes taken at the interallied conference in Paris, 26–29 November 1918. App. 300 pages.
2. Accademia dei Lincei: Archives, Correspondence to and from Volterra. Cited as “Volterra Papers”.
3. Bibliothèque de l’Observatoire de Paris (cited as “BOP”), Archives: Dossiers Baillaud (MS/1060-IV-C-1), cited as “Baillaud Papers”; Bigourdan (MS/1062-IV-1-A); BIH Archives (MS/1062-IV); Comité national français d’astronomie, CNA (MS-1062/IV-1-A. Box 115), cited as CAN Papers.
4. Bureau des Longitudes. Procès-verbaux des séances, available online at http://bdl.ahp-numerique.fr. Cited as “BDL, Procès-verbaux”.
5. Caltech Archives, Pasadena, CA: Papers of George Ellery Hale, cited as “Hale Papers”.