Não informado. (1921). Bulletin of the Astronomical Institutes of the Netherlands. Astronomical Institutes of the Netherlands.
Chicago-Zitierstil (17. Ausg.)Não informado. Bulletin of the Astronomical Institutes of the Netherlands. Amsterdam: Astronomical Institutes of the Netherlands, 1921.
MLA-Zitierstil (8. Ausg.)Não informado. Bulletin of the Astronomical Institutes of the Netherlands. Astronomical Institutes of the Netherlands, 1921.
Achtung: Diese Zitate sind unter Umständen nicht zu 100% korrekt.