Assistant of mathematics at the University of Turku, with the exception of one month of unemployment in 1971
Research assistant at the Academy of Finland
Acting associate professor of mathematics at the University of Turku
Civil service at the Academy of Finland, as the organizing secretary of the Fourth International Colloquium on Automata, Languages and Programming
Postdoctoral fellow in the Department of Applied Mathematics at McMaster University, Canada
Assistant of mathematics at the University of Turku
Lecturer of computer science at the University of Turku, excluding a period of 6 months for acting as associate professor of computer science and a 5 months leave of absence for research
Professor of computer science at the University of Kuopio
Professor of computer science at the University of Joensuu.