At the start of the 21st century , De Rijke switched to information retrieval .
During the first ten years of his scientific career Maarten de Rijke worked on formal and applied aspects of modal logic .
At the start of the 21st century , Maarten de Rijke   switched to information retrieval .
During the first ten years of his scientific career Maarten de Rijke worked on formal and applied aspects of modal logic .