About Charles Jean de la Vallée Poussin
Charles-Jean Étienne Gustave Nicolas, baron de la Vallée Poussin was a Belgian mathematician. He is best known for proving the prime number theorem. De la Vallée Poussin was awarded with Gilbert's chair when Gilbert died. While he was a professor there, de la Vallée Poussin carried out research in mathematical analysis and the theory of numbers, and in 1905 was awarded the Decennial Prize for Pure Mathematics 1894–1903. De la Vallée Poussin became a professor at the same university (as was his father, Charles Louis de la Vallée Poussin, who taught mineralogy and geology) in 1892.
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