work was not published until 1955. In a lecture at the American Mathematical Society Summer Institute in Differential Geometry (1956) in Seattle he was the first to mention deformations of complex structures and their exact relationship to cohomology. With Alfred Frölicher, he developed the Frölicher-Nijenhuis bracket (1955). Further work in this area with Roger Richardson yielded the Nijenhuis–Richardson bracket (1964). Soon thereafter his interests shifted to combinatorics. Much of his work was done with Herbert S. Wilf, with whom he published a book in 1975. After retiring, his interest in differential geometry was rekindled. His last conference presentation and paper were presented when he was nearly 70. Personal life Albert Nijenhuis became a U.S. citizen in 1959. He was married since 1955 and had four children. He died at the age of 88 after several months of failing health. Selected publications References External links University of Washington page 1926 births 2015 deaths People from Eindhoven Dutch mathematicians University of Pennsylvania faculty University of Washington faculty Fellows of the American Mathematical Society Members of the Royal Netherlands Academy of Arts and Sciences