Rare unsigned booklet: Zur Einheitlichen Feldtheorie [On the Unified Field Theory]. First edition of one of Einstein's last important scientific works. Berlin: Walter de Gruyter, 1929. Original orange printed wrappers, 7.25 x 10.25, 8 pages. In very good to fine condition, with light handling wear, and toning to the covers. By 1929, Einstein had solved the main problems he had faced in writing field equations for his unified field theory; this 'united field' theory would be a generalization of his gravitational theory, including all electromagnetic phenomena.
