This book describes a comprehensive theory of language acquisition. The core of this theory is the "input hypothesis," the notion that a language can only be learned through exposure to real human usage of it. I would like to translate it someday. Until then, feel free to check out the Japanese and ask me about anything from it.
Ch. 5 Part 1
Ch. 5 Part 2
I don't remember much about it, but this CD was how I started training my voice at around 18 or so. Probably pretty problematic in places, but I found it helpful!01 - Prologue