 Starting in the 1960s, it became increasingly common to see books including the existence of 1 in the definition of ring, especially in advanced books by notable authors such as Artin, Atiyah and MacDonald, Bourbaki, Eisenbud, and Lang.But even today, there are many books that do not require a 1.Faced with this terminological ambiguity, some authors have tried to impose their views, while others have tried to adopt more precise terms.