He then moved back to his home town to take up a professorship of mathematics in 1565 .

He returned to Finland in 1938 to take up a professorship at the University of Helsinki.

He remained at Michigan until 1960, when he returned to Harvard to take up a professorship.

In 1987 he took up a professorship for mathematics at the University of Namibia.

Seven years later, he took up a professorship there.

In 1948 she took up a professorship at Harvard, a position she held until her retirement in 1954.

On his official retirement he took up a professorship at Kanagawa University.

Oxford remained his academic home until 2005 when he took up a professorship at the University of Sheffield.

In 1986 he took up a professorship at the University of Bonn.

In 1866 he took up a professorship at the University of Tübingen.