Field of study: Astronomy

• On the luminosity of the fixed stars
  KNAW, Proceedings, 3, 1900-1901, Amsterdam, 1901, pp. 658-689
  
  
• On the mean star-density at different distances from the solar system
  KNAW, Proceedings, 10 II, 1907-1908, Amsterdam, 1908, pp. 626-635
  
  
• On the parallax of the nebulae
  KNAW, Proceedings, 8 II, 1905-1906, Amsterdam, 1906, pp. 691-699
  
  
• Reply to the criticism of Dr. J. Stein, S.J
  KNAW, Proceedings, 4, 1901-1902, Amsterdam, 1902, pp. 232-242
  
  
• Star systems and the milky way
  KNAW, Proceedings, 14 II, 1911-1912, Amsterdam, 1912, pp. 909-911
  
  
• The determination of the Apex of the Solar motion
  KNAW, Proceedings, 2, 1899-1900, Amsterdam, 1900, pp. 353-374
  
  
• The Milky way and the star-streams
  KNAW, Proceedings, 14 I, 1911, Amsterdam, 1911, pp. 524-530