journal articles with 266 coauthors. His main interests lie in mathematical logic, model theory in particular, and in axiomatic set theory. In model theory, he developed classification theory, which led him to a solution of Morley's problem. In set theory, he discovered the notion of proper forcing, an important tool in iterated forcing arguments. With PCF theory, he showed that in spite of the undecidability of the most basic questions of cardinal arithmetic (such as the continuum hypothesis), there are still highly nontrivial ZFC theorems about cardinal exponentiation. Shelah constructed a Jónsson group, an uncountable group for which every proper subgroup is countable. He showed that Whitehead's problem is independent of ZFC. He gave the first primitive recursive upper bound to van der Waerden's numbers V(C,N). He extended Arrow's impossibility theorem on voting systems. Shelah's work has had a deep impact on model theory and set theory. The tools he developed for his classification theory have been applied to a wide number of topics and problems in model theory and have led to great advances in stability theory and its uses in algebra and algebraic geometry as shown for example by Ehud Hrushovski and many others. Classification theory involves deep work developed in many dozens of papers to completely solve the spectrum problem on classification of first order theories in terms of structure and number of nonisomorphic models, a huge tour de force. Following that he has extended the work far beyond first order theories, for example for abstract elementary classes. This work also has had important applications to algebra by works of Boris Zilber. Awards Three times speaker at the International Congress of Mathematicians (1974 invited, 1983 plenary, 1986 plenary) The first recipient of the Erdős Prize, in 1977 The Karp Prize of the Association for Symbolic Logic in 1983 The Israel Prize, for mathematics, in 1998 The Bolyai Prize in 2000 The Wolf Prize in Mathematics in 2001 The EMET Prize for Art, Science and Culture in 2011 The Leroy P. Steele Prize, for Seminal Contribution to Research, in 2013 Honorary member of the Hungarian Academy of Sciences, in 2013 Advanced grant of the European Research Council (2013) Hausdorff Medal of the European Set Theory Society, joint with Maryanthe Malliaris, 2017 Schock Prize in Logic and Philosophy of the Royal Swedish Academy of Sciences, 2018 Honorary doctorate from the Technische Universität Wien, 2019 Selected works Proper forcing, Springer