Siegfried Flügge was a prominent physicist who made significant contributions to theoretical nuclear physics and quantum mechanics. Born in 1912 in Dresden, he studied physics in Dresden, Frankfurt, and Göttingen, where he earned his doctorate in 1933 under the supervision of Max Born. He worked in Berlin as a theorist-in-residence with Otto Hahn and Lise Meitner, witnessing the discovery of nuclear fission. Flügge held academic positions in Königsberg, Göttingen, and Marburg before moving to Freiburg in 1961, where he taught until his retirement in 1977. He died in 1997. Flügge's work spanned theoretical nuclear physics, quantum physics, astrophysics, and other areas. He authored numerous textbooks that became standard references for students. He also edited the monumental Encyclopedia of Physics. His book "Practical Quantum Mechanics" is a classic in mathematics, first published in 1947 in German. The English edition, published in two volumes in 1971, was intended to serve as a practical guide for students and scientists. The second edition, published in 1994, was expanded to include new approximation methods and developments in scattering theory, as well as relativistic quantum mechanics and radiation theory. The book includes a comprehensive set of problems and solutions, with an emphasis on practical applications of quantum mechanics. The second volume of the book covers particles with spin, two- and three-body problems, many-body problems, and non-stationary problems. The book also includes a mathematical appendix with special functions and coordinate systems. The work has been widely used and praised for its clarity and practical approach to quantum mechanics.Siegfried Flügge was a prominent physicist who made significant contributions to theoretical nuclear physics and quantum mechanics. Born in 1912 in Dresden, he studied physics in Dresden, Frankfurt, and Göttingen, where he earned his doctorate in 1933 under the supervision of Max Born. He worked in Berlin as a theorist-in-residence with Otto Hahn and Lise Meitner, witnessing the discovery of nuclear fission. Flügge held academic positions in Königsberg, Göttingen, and Marburg before moving to Freiburg in 1961, where he taught until his retirement in 1977. He died in 1997. Flügge's work spanned theoretical nuclear physics, quantum physics, astrophysics, and other areas. He authored numerous textbooks that became standard references for students. He also edited the monumental Encyclopedia of Physics. His book "Practical Quantum Mechanics" is a classic in mathematics, first published in 1947 in German. The English edition, published in two volumes in 1971, was intended to serve as a practical guide for students and scientists. The second edition, published in 1994, was expanded to include new approximation methods and developments in scattering theory, as well as relativistic quantum mechanics and radiation theory. The book includes a comprehensive set of problems and solutions, with an emphasis on practical applications of quantum mechanics. The second volume of the book covers particles with spin, two- and three-body problems, many-body problems, and non-stationary problems. The book also includes a mathematical appendix with special functions and coordinate systems. The work has been widely used and praised for its clarity and practical approach to quantum mechanics.