Ken Freeman, Geoff McNamara (2006). In Search of Dark Matter. Springer. ISBN978-0-387-27616-8. "the story of the emergence of the dark matter problem, from the initial 'discovery' of dark matter by Jan Oort"
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van de Hulst, H. C. (1994), "Jan Hendrik Oort (1900–1992)", Quarterly Journal of the Royal Astronomical Society, 35 (2): 237–242, Bibcode:1994QJRAS..35..237V.