lord of the rings - In which of Tolkien's works does the Witch-King of Angmar appear?

Where can I read all about the Witch-King of Angmar? Does he appear anywhere other than the Lord of the Rings trilogy and its appendices?

The appendices talk about the Angmar vs Arnor war very vaguely and without detail. In online wikis there is tons of information about this war, and if I recall correctly it lasted over 400 years. Where can I find the source of this information, assuming that the extreme detail in the wiki was not simply made up. LOTR itself? The Hobbit (unlikely)? History of Middle Earth? The Unfinished Tales? The Silmarillion? Does anyone know?