Author J.K. Rowling is trying to stop a fan from publishing a "Harry Potter" encyclopedia, citing violation of her copyrights, media reported today.

Rowling is scheduled to testify today in US District Court in Manhattan. She brought the lawsuit last year against Vander Ark's publisher, RDR Books, to stop publication of the "Harry Potter Lexicon."

The author said her copyrights would be violated if Vander Ark's publisher is allowed to publish the encyclopedia.

One of her lawyers, Dan Shallman, on Friday told Judge Robert P. Patterson, who will hear the trial without a jury, that Rowling "feels like her words were stolen."

Rowling is actually a big fan of the Harry Potter Lexicon website that Vander Ark runs. But she draws the line when it comes to publishing the book and charging US$24.95.

In court papers, Vander Ark, 50, said he initially declined proposals to convert the website into an encyclopedia, but an RDR Books employee told him that publication of the lexicon would not violate copyright law.

Still, to protect himself, Vander Ark said he insisted that RDR Books includes a clause in his contract that the publisher would defend and pay any damages that might result from claims against him.

Rowling published her seventh and final book in the Harry Potter series eight months ago. More than 400 million copies of the books have been sold.