(2015). Plunkett Analytics Reports. Book Stores Industry (US). Plunkett Research, Ltd..
Lua i Stíl Chicago (17ú heag.)Plunkett Analytics Reports. Book Stores Industry (US). [S.l.]: Plunkett Research, Ltd., 2015.
Lua MLA (9ú heag.)Plunkett Analytics Reports. Book Stores Industry (US). Plunkett Research, Ltd., 2015.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.