The Index librorum prohibitorum ("List of Prohibited Books") was a list of publications deemed heretical or contrary to morality by the Sacred Congregation of the Index (a former Dicastery of the Roman Curia), and Catholics were forbidden to read them without permission.. There were attempts to censor individual books before the sixteenth century, notably the ninth-century Decretum Glasianum On June 14, 1966, the Roman Catholic Church abolished their famous list of banned books, the Index Librorum Prohibitorum or shorter simply, the Index, that had been installed almost 500 years ago.Actually, it was soon clear after the invention of the printing press that the written word could also be dangerous, especially if it can be published in large quantities.