 Peirce’s two-decade work made a major contribution to the algebra of logic tradition in two important ways. First, Peirce’s introduction of quantifiers and variables itself is a significant advance in formal logic, close to the predicate logic we know. Second, subsequent momentous work on mathematical logic was built on the new notation and extended logic by Peirce and his students, O. H. Mitchell and C. Ladd (later Ladd-Franklin). A decade after Peirce’s “On the Algebra of Logic”, (1885) Ernst Schröder published three volumes of mathematical logic Vorlesungen über die Algebra der Logik  (1890–1905).[19]  His work was carried out squarely in the Boolean algebraic tradition, and two important aspects of the book reflect Peirce’s influence: He adopted Peirce’s notation (over Frege’s), and the third volume is devoted to the logic of relations. Goldfarb’s insightful paper expresses these two aspects of Peirce’s influence in the following way: