Files Go - media player
The Fono method relies heavily on audio. The books were designed to be used in tandem with cassettes or CDs. A PDF downloaded from a file-sharing site almost never comes with the corresponding audio files. Learning German from a text-only PDF is like trying to learn to play the piano by reading sheet music without ever touching the keys. You miss the crucial component of pronunciation and listening comprehension, which Fono actually excelled at teaching.