As a volunteer, the wisest thing to do is to choose a book published before 1923. It is also required that copyright clearance be confirmed prior to working on any book by sending a photocopy of the title page and verso page (even if the latter is blank) to Michael Hart. The pages should be sent as scans to be uploaded on the website. For people who cannot create scans, it is possible to send photocopies by postal mail. The pages will then be filed, either on paper or electronically, so that the proof will be available in the future, to demonstrate if necessary that the book is in the public domain under the US law. Project Gutenberg doesn't release any book until the book's copyright status has been confirmed. What is entailed exactly, once copyright clearance is received? Digitization is done by scanning the book page after page to get "image" files. Then volunteers run an OCR (Optical Character Recognition) software to convert "image" files into text files. Then each text file is proofread (i.e. re-read and corrected) by comparing it to the "image" file or the original page of the print version. There is an average of 10 mistakes per page for a good OCR package, and many more mistakes if the quality of the scanner and the OCR package is not great. The book is proofread twice on the computer screen by two different people, who make any corrections necessary. When the original is in poor condition, as with very old books, it is keyed in manually, word by word. Some volunteers themselves prefer to type short texts, or works they particularly like. But most books are scanned, "OCRized" and proofread. Contrary to digitization in "image format", which consists only in scanning the pages, digitization in "text format" adds the OCR step: a) the book can be copied, indexed, searched, analyzed and compared with other books; b) it is possible to search the content of the book with the "Find" button available in any browser and any software, without a specific search engine. The assets of digitization in "text format" are numerous. It makes a smaller and more easily sendable computer file, unlike digitization in "image format", which produces a bulky "photo" file. Contrary to other formats, the files are accessible for low-bandwidth use. They can be copied as much as needed to produce new digital or print versions for free. The typos pointed out after the text is released can be fixed at any time. Readers can change the font and size of characters, the margins or the number of lines per page. Visually impaired readers can increase the letter size. Blind readers can use speech recognition software. All this is very difficult, if not impossible, with many other formats. If the books released are 99.9% accurate in the eyes of the general reader, the goal is not to create authoritative editions, and to argue with a picky reader whether a certain sentence should have a colon instead of a semi-colon between its clauses.