 There is a sizeable literature on paradoxes already in the early years of the 20th century, which is not at all exhausted by the previous discussion. Refinements and variations of foundational and logical interest are to be found in the works of several authors, including prominent mathematicians, among them Peano, Borel, Schönflies, Brouwer, and Weyl. Some of the more stimulating and original proposals are surveyed in the rest of this section.