Quarto (abbreviated 4to or 4°) is a technical term describing the format of a book, which refers to the size of leaves produced from folding a full sheet of paper on which multiple pages of text were printed to form the individual sections (or gatherings) of a book. A quarto is a book or pamphlet made up of one or more full sheets of paper on which 8 pages of text were printed, which were then folded two times to produce four leaves. Each leaf of a quarto book thus represents one fourth the size of the original sheet. Other common book formats are folios and octavos. The earliest known European printed book is a quarto, the Sibyllenbuch, believed to have been printed by Gutenberg in 1452-53, before the Gutenberg Bible, surviving only as a fragment. Quarto is also used as a general description of size of books that are about 12 inches tall, and as such does not necessarily indicate the actual printing format of the books, which may even be unknown as is the case for many modern books. These terms are discussed in greater detail in Book sizes.