The CULP method for writing the Lakȟóta language is based upon a modified form of the Americanist Phonetic Notation. The APN can be found on Wikipedia, as are references to Unicode and the International Phonetic Alphabet. These resources provide free and available information to anyone who wishes to use them.
Below is text that I recently posted on Lakota Word of the Day on FaceBook.
(Click on the image below in order to view the larger, original size of the image.)