The Aarne–Thompson Tale Type Index divides tales into sections with an AT number for each entry. The names given are typical, but usage varies; the same tale type number may be referred to by its central motif or by one of the variant folktales of that type, which can also vary, especially when used in different countries and cultures. The name does not have to be strictly literal for every folktale. For example, "The Cat as Helper" (545B) also includes tales where a fox helps the hero. Closely related folktales are often grouped within a type. For example, tale types 400–424 all feature brides or wives as the primary protagonist, for instance "The Quest for a Lost Bride" (400) or the "Animal Bride" (402). Subtypes within a tale type are designated by the addition of a letter to the AT number, for instance: tale 510, "Persecuted Heroine" (renamed in Uther's revision as "Cinderella and Peau d'Âne"), has subtypes 510A, "Cinderella", and 510B, "Catskin" (renamed in Uther's revision as "Peau d'Asne").