In the article: S Mandelbrojt, Souvenirs à bâtons rompus de Szolem Mandelbrojt recueillis en 1970 et préparés par Benoit Mandelbrot, Cahiers du Séminaire d'histoire des Mathématiques 6 (1985), 1-46 Szolem Mandelbrojt talks with his nephew Benoit Mandelbrot. He showed a family photograph to his nephew who replied:-

I remember several of your visits to Warsaw. Most of all thanks to this family photograph, with Hadamard, Montel, Denjoy and you, and (in full view) what was said to be the only bottle of Bordeaux to be found in the whole of Warsaw. You were on your way to Moscow.

Szolem Mandelbrojt then explained some details of the visit to Moscow, via Poland, and recounted some interesting family details in the process:-

Yes, it was very interesting, and even now, those who are still alive, Montel and Denjoy, remember all that. In 1930, there was a congress of Russian mathematicians in Kharkov and the Russians had invited these four mathematicians [Hadamard, Montel, Denjoy and Mandelbrojt] from France. Goncharov came for us at the border and took us to Kharkov. But we passed through Warsaw. I don't know which one of us told the Polish mathematicians; Sierpinski came to meet us at the station. My father, who was a handsome old man with a long white beard, was very happy, very honoured, to invite French mathematicians. Although they had been invited by Polish mathematicians, they preferred to go to my father's house and my father really gave them a very good reception. I still remember the letters Montel wrote to me about the handsomeness of this old man, and Hadamard talked a lot about him to me. We dined at my father's, my sisters were there, your [Benoit Mandelbrot] father was there.

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