with the critic Charles Du Bos. Together they were part of the Foyer Franco-Belge, in which capacity they worked to find employment, food and housing for Franco-Belgian refugees who arrived in Paris following the German invasion of Belgium. Their friendship later declined, due to Du Bos' perception of Gide as disavowing or betraying his spiritual faith, in contrast to Du Bos' own return to faith. Du Bos' essay Dialogue avec André Gide was published in 1929. The essay, informed by Du Bos' Catholic convictions, condemned Gide's homosexuality. Gide and Du Bos' mutual friend Ernst Robert Curtius criticised the book in a letter to Gide, writing that "he [Du Bos] judges you according to Catholic morals suffices to neglect his complete indictment. It can only touch those who think like him and are convinced in advance. He has abdicated his intellectual liberty." In the 1920s, Gide became an inspiration for writers such as Albert Camus and Jean-Paul Sartre. In 1923, he published a book on Fyodor Dostoyevsky; however, when he defended homosexuality in the public edition of Corydon (1924) he received widespread condemnation. He later considered this his most important work. In 1923, he sired a daughter, Catherine, by Elisabeth van Rysselberghe, a woman who was much younger than he. He had known her for a long time, as she was the daughter of his closest female friend, Maria Monnom, the wife of his friend the Belgian neo-impressionist painter Théo van Rysselberghe. This caused the only crisis in the long-standing relationship between Allégret and Gide and damaged the relation with van Rysselberghe. This was possibly Gide's only sexual relationship with a woman, and it was brief in the extreme. Catherine became his only descendant by blood. He liked to call Elisabeth "La Dame Blanche" ("The White Lady"). Elisabeth eventually left her husband to move to Paris and manage the practical aspects of Gide's life (they had adjoining apartments built for each on the rue Vavin). She worshiped him, but evidently they no longer had a sexual relationship. Gide's legal wife, Madeleine, died in 1938. Later he explored their unconsummated marriage in his memoir of Madeleine, Et nunc manet in te. In 1924, he published an autobiography, If it Die... (French: Si le grain ne meurt). In the same year, he produced the first French language editions of Joseph Conrad's Heart of Darkness and Lord Jim. After 1925, he began to campaign