Question: What is the ranking of the school sometimes called UCL, that employed Paul Cohn, among the world's best colleges and universities?

full_context: Document 1: London: There are a number of business schools in London, including the London School of Business and Finance, Cass Business School (part of City University London), Hult International Business School, ESCP Europe, European Business School London, Imperial College Business School and the London Business School. London is also home to many specialist arts education institutions, including the Academy of Live and Recorded Arts, Central School of Ballet, LAMDA, London College of Contemporary Arts (LCCA), London Contemporary Dance School, National Centre for Circus Arts, RADA, Rambert School of Ballet and Contemporary Dance, the Royal College of Art, the Royal College of Music and Trinity Laban.
Document 2: Alfred Menezes: Alfred Menezes is co-author of several books on cryptography, including the "Handbook of Applied Cryptography", and is a professor of mathematics at the University of Waterloo in Canada.
Document 3: London: A number of universities in London are outside the University of London system, including Brunel University, City University London, Imperial College London, Kingston University, London Metropolitan University, Middlesex University, University of East London, University of West London and University of Westminster, (with over 34,000 students, the largest unitary university in London), London South Bank University, Middlesex University, University of the Arts London (the largest university of art, design, fashion, communication and the performing arts in Europe), University of East London, the University of West London and the University of Westminster. In addition there are three international universities in London – Regent's University London, Richmond, The American International University in London and Schiller International University.
Document 4: London School of Economics: LSE is located in Westminster, central London, near the boundary between Covent Garden and Holborn. The area is historically known as Clare Market. The LSE has more than 10,000 students and 3,300 staff, just under half of whom come from outside the UK. It had a consolidated income of £340.7 million in 2015 / 16, of which £30.3 million was from research grants. One hundred and fifty five nationalities are represented amongst LSE's student body and the school has the highest percentage of international students (70%) of all British universities. Despite its name, the school is organised into 25 academic departments and institutes which conduct teaching and research across a range of legal studies and social sciences.
Document 5: Martin Aigner: He received Ph.D from the University of Vienna. His book "Proofs from THE BOOK" (co-written with Günter M. Ziegler) has been translated into 12 languages.
Document 6: London: London is home to five major medical schools – Barts and The London School of Medicine and Dentistry (part of Queen Mary), King's College London School of Medicine (the largest medical school in Europe), Imperial College School of Medicine, UCL Medical School and St George's, University of London – and has a large number of affiliated teaching hospitals. It is also a major centre for biomedical research, and three of the UK's five academic health science centres are based in the city – Imperial College Healthcare, King's Health Partners and UCL Partners (the largest such centre in Europe).
Document 7: John von Neumann: Additionally, "[I]n the general case, von Neumann proved the following basic representation theorem. Any complemented modular lattice L having a "basis" of n≥4 pairwise perspective elements, is isomorphic with the lattice ℛ(R) of all principal right-ideals of a suitable regular ring R. This conclusion is the culmination of 140 pages of brilliant and incisive algebra involving entirely novel axioms. Anyone wishing to get an unforgettable impression of the razor edge of von Neumann's mind, need merely try to pursue this chain of exact reasoning for himself—realizing that often five pages of it were written down before breakfast, seated at a living room writing-table in a bathrobe."
Document 8: Mark Ronan: Mark Andrew Ronan (born 1947) is Emeritus Professor of Mathematics at the University of Illinois at Chicago and Honorary Professor of Mathematics at University College London. He has lived and taught in: Germany (at the University of Braunschweig and the Free University of Berlin); in England, where from 1989 to 1992 he was Mason Professor of Mathematics at the University of Birmingham; and America at the University of Illinois at Chicago, where his teaching included courses on ancient literature from Mesopotamia, and on the history of the calendar, as well as mathematics.
Document 9: Sheldon Axler: Sheldon Jay Axler (born 6 November 1949, Philadelphia) is an American mathematician, professor of mathematics and the Dean of the College of Science and Engineering at San Francisco State University. He has made contributions to mathematics education, publishing several mathematics textbooks.
Document 10: London: A number of world-leading education institutions are based in London. In the 2014/15 QS World University Rankings, Imperial College London is ranked joint 2nd in the world (alongside The University of Cambridge), University College London (UCL) is ranked 5th, and King's College London (KCL) is ranked 16th. The London School of Economics has been described as the world's leading social science institution for both teaching and research. The London Business School is considered one of the world's leading business schools and in 2015 its MBA programme was ranked second best in the world by the Financial Times.
Document 11: Paul Cohn: Paul Moritz Cohn FRS (8 January 1924 – 20 April 2006) was Astor Professor of Mathematics at University College London, 1986-9, and author of many textbooks on algebra. His work was mostly in the area of algebra, especially non-commutative rings.
Document 12: Cole Prize: The Frank Nelson Cole Prize, or Cole Prize for short, is one of two prizes awarded to mathematicians by the American Mathematical Society, one for an outstanding contribution to algebra, and the other for an outstanding contribution to number theory. The prize is named after Frank Nelson Cole, who served the Society for 25 years. The Cole Prize in algebra was funded by Cole himself, from funds given to him as a retirement gift; the prize fund was later augmented by his son, leading to the double award.
Document 13: John von Neumann: Von Neumann introduced the study of rings of operators, through the von Neumann algebras. A von Neumann algebra is a *-algebra of bounded operators on a Hilbert space that is closed in the weak operator topology and contains the identity operator. The von Neumann bicommutant theorem shows that the analytic definition is equivalent to a purely algebraic definition as an algebra of symmetries. The direct integral was introduced in 1949 by John von Neumann. One of von Neumann's analyses was to reduce the classification of von Neumann algebras on separable Hilbert spaces to the classification of factors.
Document 14: London: London is a major global centre of higher education teaching and research and its 43 universities form the largest concentration of higher education institutes in Europe. According to the QS World University Rankings 2015/16, London has the greatest concentration of top class universities in the world and the international student population around 110,000 which is also more than any other city in the world. A 2014 PricewaterhouseCoopers report termed London as the global capital of higher education
Document 15: London: With 120,000 students in London, the federal University of London is the largest contact teaching university in the UK. It includes four large multi-faculty universities – King's College London, Queen Mary, Royal Holloway and UCL – and a number of smaller and more specialised institutions including Birkbeck, the Courtauld Institute of Art, Goldsmiths, Guildhall School of Music and Drama, the Institute of Education, the London Business School, the London School of Economics, the London School of Hygiene & Tropical Medicine, the Royal Academy of Music, the Central School of Speech and Drama, the Royal Veterinary College and the School of Oriental and African Studies. Members of the University of London have their own admissions procedures, and some award their own degrees.
ground_truth: 5th
sub_queries: Paul Cohn >> employer Answer: University College London
Where is University College London , or UCL, ranked among the world's best colleges and universities? Answer: 5th