Dialogue concerning the two chief world systems Ptolemaic & Copernican by Galilei Galileo 2d. ed Copyright Year: 1967 ISBN-13: 9780520004504 Available format(s): Classic Audio Log in to read What's an Audio Format Audio format refers to the way an audiobook is recorded. Not all audiobooks have the same formats. Classic Audio: A human reading an audiobook without the text displayed. VOICEtext (H): Human narrator with text that you can follow along with as it reads. VOICEtext (S): Synthetic voice with text you can follow along with as it reads.