This is always a hotly disputed area, and there is no agreed set of values. Aspects of the audience of a work -- the readership -- can affect the language, and the relationship between writer and reader. Style is typical of the kind of classification that is almost certainly driven by internal criteria rather than external, and the unsatisfactory state of the classifications so far (e.g. Joos, 1961) points this up. Style will be treated in detail below under internal criteria.