This past July, I wrote a post about Enrico Delle Sedie, a leading voice teacher in Paris who's works were published in America by the Boston publisher Oliver Ditson. While Delle Sedie's books are hard to find outside a library, a google search reveals several journal articles worth reading.  

Here is one titled "How To Learn To Sing."  I'd be please to know what you make of it.

Worth noting is Delle Sedie's instruction from the 'masters of old'.  In order to obtain a rounded and broad vowel one must "Swell the sound in the mouth by raising the thorax."  Now that's something to ponder. Equally provocative is Delle Sedie's instruction to sing mezza voice (half voice) in the middle of the voice to obtain control over it, only afterwards developing volume.   I use the word provocative because it's a method which takes time, and time is in short supply when a large voice is the only goal.