Wilfrid Voynich was a Polish-American antiquarian who is best known for acquiring the Voynich Manuscript in 1912. He was a dealer in rare books and manuscripts, and his collection included many important items. However, he did not write the Voynich Manuscript.
The Voynich Manuscript is an illustrated codex written in an unknown script and language, and its contents have been the subject of much speculation and debate. It is considered one of the most enigmatic books in the world.
While Voynich didn't write the Voynich Manuscript, he did write a book about it: "The Voynich Manuscript: A Study in the Art of Writing" (published posthumously in 1978). This book contains his research and observations about the manuscript, but it does not offer a definitive solution to its mysteries.
So, to answer your question, Wilfrid Voynich's known written work consists only of his book about the Voynich Manuscript.