The university is spread across four campuses in the Netherlands – the City Centre Campus, the Roeterseiland Campus, the Amsterdam Science Park and the Academic Medical Center. In a recent year, more than 30,000 students attended the university. Tuition at the Dutch institution is higher for students from non-European Union and non-European Economic Area countries, with the exception of Swiss and Surinamese students. The university reserves a number of rooms for international students in residences that outside housing organizations manage. The university has seven academic divisions: dentistry, economics and business, humanities, law, medicine, science, and social and behavioral sciences. The school's academic calendar is semester-based. The primary language of instruction for bachelor’s programs is Dutch, though several English-taught programs are available. Many master's programs are taught in English. Around one-fourth of the University of Amsterdam's research is conducted in one of the institution’s 20 research priority areas, which include infection and immunity, behavioral economics, and private and public European law. Some of the university’s research institutes include the Amsterdam Institute for Advanced Labour Studies, the Institute for Biodiversity and Ecosystem Dynamics and the Anton Pannekoek Institute for Astronomy. The university also manages two institutes – one in Athens, Greece, and the other in Saint Petersburg, Russia – that are members of the Dutch Scientific Institutes Abroad network. The institutes support Dutch staff and students who conduct research overseas.