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 [1].

Wikipedia page, created 2007 and still present October 2017, and partly wound down October 2018, here [2] - there is a link to his other articles on the VM.

His website (which is undated) is here [3]. (Checked October 2018)