Chapter 2 presents a review of earlier studies that were mostly based on the assumption that general extenders are used with a referential function, are content-oriented, signal categorization and can be analyzed as set-marking tags or vague category identifiers. In the clearest cases, which are typically longer forms, they can be analyzed in terms of semantic features, shared with an antecedent, that identify the category involved. In other cases, there may be reference to an ad hoc category, also described as a non-lexicalized category, rather than one that is already lexicalized. The use of adjunctive forms as list completers is also normally interpreted in terms of set-marking.Adjunctive forms are also shown to be indicators of intertextuality. Long forms described as SKT tags incorporate reference to a "kind," indicating that classification or categorization is being signaled. A final section is dedicated to specific extenders, typically used with clear referential function.