In 2003 Jan Hurych located a document signed by Jacobus Sinapius: the signature did not match that in the Voynich Manuscript.
His article of 20th July, 2009, 'Voynich Now and then' on Wilfrid Voynich's article of 1921, can be found here.
Wikipedia page, created 2007, still present October 2017, and partly wound down October 2018, here [1] - there is a link to his other articles on the VM.
His website (which is undated), in Czech (the English version is no longer available) is here. (Checked June 2022).