Versor Algebra as Applied to Polyphase Power Systems by Eric P. Dollard. Look at both posts. Although this is posted for free – it is just part of the new book, more to come… consider paying for a copy when the entire book is complete to support Eric’s work!

http://www.energeticforum.com/253951-post1860.html

http://www.energeticforum.com/253952-post1861.html