I almost broke the law without knowing there even was a law.
A couple of weeks ago, I tweeted about the first "iText in Action" review on Amazon:
This tweet started a mail conversation about books. I explained that my first book was stored in the Library of Congress, but that in Belgium only the library of Ghent University had a copy (because I donated one). I received an immediate reply: in Belgium all books printed by Belgian publishers or written by Belgian authors are stored in the Koninklijke Bibliotheek van België / Bibliothèque royale de Belgique.
I visited the site and I found out that there's a law (dating from 2008) that states that every Belgian publisher has the obligation to donate two copies of each title to the library. If a Belgian author publishes a book with a foreign publisher, then it's the obligation of the author to donate two copies. I didn't know that. I could have sent the books by mail free of charge, but as I didn't know of the existence of the Royal Library, I decided to visit the Royal Library:
I received two pages with a stamp, one for my first book (dating from before the law) and one for the second edition. Now the Belgian state can no longer deny that I'm an author. I'll add a copy of the stamped forms to my tax form and I'll send a copy to the social security so that I no longer have to pay too much taxes on my royalties ;-)