(Text)Books for voice & speech development
You may download them using the Library of Genesis (the pirate way) or google the names and buy/rent them (the honest way).
The Second Circle by Patsy Rodenburg;
Actor Training The Laban Way: An Integrated Approach to Voice, Speech, and Movement by Barbara Adrian;
Pronouncing Dictionary of American English by John S. Kenyon and Thomas A. Knott;
Freeing the Natural Voice by Kristen Linklater;
Voice: Onstage and Off by Robert Barton and Rocco Dal Vera;
Public Speaking by Michael Osborn & Susanne Osborn, 8th Edition.
For those with Russian as mother tongue:
Speaking clearly. Improving voice and articulation: Фонетический практикум by Фомиченко Л.Г.

















