LEBESGUE, Leçons sur les séries trigonométriques, 1906

First edition.
Henri Lebesgue (1875-1941), is one of the great French mathematicians of the first half of the twentieth century. He is recognized for his theory of integration and for his theory of measurement, which extends the important early work of Émile Borel.

His lessons on trigonometric series repeat the courses given in 1904-1905 at the Collège de France.