A cover, normally made of limp vellum or similar flexible material, with overlapping flaps on all three edges to protect pages from damage or soiling. The style was developed by William Yapp in the 19th century.
Encuadernación a tres tapas
Matt T. Roberts and Don Etherington, Bookbinding and the Conservation of Books: A Dictionary of Descriptive Terminology (Washington, DC: Library of Congress, 1982).
John Carter and Nicolas Barker, ABC for Book Collectors, 8th edition (New Castle, DE: Oak Knoll Press, 2004).