↑"Kai Siegbahn, Swedish Physicist, Dies at 89". The New York Times. August 7, 2007. Kai Siegbahn, a Swedish physicist whose work in developing a novel technique using electrons to test the composition and purity of materials won a Nobel Prize in 1981, died on July 20. He was 89 and had been visiting his summer home in Ängelholm, in southern Sweden.{{cite news}}: |access-date= requires |url= (help); Cite has empty unknown parameter: |coauthors= (help)
