Bibliography (from Greek , bibliographia, literally "book writing"), as a discipline, is traditionally the academic study of books as physical, cultural objects; in this sense, it is also known as bibliology (from Greek , -logia). Carter and Barker (2010) describe bibliography as a twofold scholarly discipline -- the organized listing of books (enumerative bibliography) and the systematic, detailed description of books as physical objects (descriptive bibliography). These two distinct concepts and practices have separate rationales and serve differing purposes. Innovators and originators in the field include W. W. Greg, Fredson Bowers, Philip Gaskell, and G. Thomas Tanselle.