Walter Ripman, The Sounds of Spoken English: A Manual of Ear Training for English Students
“ It is above all the teacher who is constantly brought face to face with some difficulty on the part of a pupil. He realises that something is wrong in the pronunciation of a word, but he cannot clearly tell where the fault lies; he trusts that improvement will follow if he repeatedly utters the word correctly pronounced and gets the pupil to say it after him. To his distress the pupil still says the word in the old way, and at last the teacher gives up in despair. When a foreign language is attempted, the difficulties become even more apparent ”
