Não informado. Publications of the Kapteyn Astronomical Laboratory at Groningen. University of Groningen.
Chicago-viite (17. p.)Não informado. Publications of the Kapteyn Astronomical Laboratory at Groningen. Groningen, Holanda: University of Groningen.
MLA-viite (8. p.)Não informado. Publications of the Kapteyn Astronomical Laboratory at Groningen. University of Groningen.
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