Luitingh-Sijthoff, a Dutch publishing company passed down through the Sijthoff family
The family's publishing company continues to operate today as Luitingh-Sijthoff.
In an article in Quote in July 2006, Jort Kelder states that a confidant of Willem Endstra told him that Sijthoff bought two pit houses in Amsterdam from Endstra in March 2001 through the mediation of Willem Holleeder.
Bob Sijthoff, descendant of Albertus Willem Sijthoff who sued Wikimedia in the Netherlands in 2008
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Albert Georg Sijthoff (1853–1927), son of Albertus Willem Sijthoff and publisher of the Haagsche Courant