Riemann's theory of trigonometrical series 11.1. The Cantor-Lebesgue theorem and its generalization. 11.2. Riemann's and Fatou's theorems. 11.3. Theorems of uniqueness. 11.4. The principle of localization. Rajchman's theory of formal multiplication. 11.5. Sets of uniqueness and sets of multiplicity. 11.6. Uniqueness in the case of summable series. 11.7. Miscellaneous theorems and examples.