Mainly these concerned the lack of communication between Russia and the West so that he was unaware of results of Weyl and others which was highly relevant to his work and similarly mathematicians in the West were largely unaware of Vinogradovs results

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Mainly these concerned the lack of communication between Russia and the West so that he was unaware of results of Weyl and others which was highly relevant to his work and, similarly, mathematicians in the West were largely unaware of Vinogradov's results.