The exploration of binding phenomena got started in the 1970s and interest peaked in the 1980s with Government and Binding Theory, a grammar framework in the tradition of generative syntax that is still prominent today. The theory of binding that became widespread at that time serves now merely as reference point (since it is no longer believed to be correct). This theory distinguishes between 3 different binding conditions: A, B, and C. The theory classifies nominals according to two features, [±anaphor] and [±pronominal], which are binary. The binding characteristics of a nominal are determined by the values of these features, either plus or minus. Thus, a nominal that is [-anaphor, -pronominal] is an R-expression (referring expression), such as a common noun or a proper name. A nominal that is [-anaphor, +pronominal] is a pronoun, such "he" or "they", and a nominal that is [+anaphor, -pronominal] is a reflexive pronoun, such as "himself" or "themselves". Note that the term "anaphor" here is being used in a specialized sense; it essentially means "reflexive". This meaning is specific to the Government and Binding framework and has not spread beyond this framework.