As per the title, an excellent resource on modifying one`s voice towards congruency; written by two of the United Kingdom`s leading voice experts (Mathew Mills and Gillie Stoneham).
I found its well written, considered content and approach, to be very informative and usefully applied in practice.
"The Voice Book for Trans and Non-Binary People - A practical guide to creating and sustaining authentic voice and communication"Jessica Kingsley Publishers (London and Philadelphia)
ISBN 978-1-78592-128-5
http://www.jkp.com/uk/the-transgender-experience-2.htmlAvailable at Amazon and other online vendors