The University of Cologne (German Universität zu Köln) is one of the oldest universities in Europe and, with over 44,000 students, one of the largest universities in Germany. The university is part of the Deutsche Forschungsgemeinschaft, an association of Germany's leading research universities. It is furthermore the German founding member of the Community of European Management Schools and International Companies (CEMS). The University of Cologne was established in 1388 as the fourth university in the Holy Roman Empire, after the Charles University of Prague (1348), the University of Vienna (1365) and the Ruprecht Karl University of Heidelberg (1386). The charter was signed by Pope Urban VI. The university began teaching on January 6, 1389. In 1798, the university was abolished by the French, who had invaded Cologne in 1794, because its professors, wishing to preserve their university’s independence, refused to swear an oath of allegiance to the French First Republic. However, the last rector Ferdinand Franz Wallraf hid and so preserved the university’s Great Seal, now once more in use.