A practical guide. Chichester, West Sussex: Wiley-Blackwell.
• Seliger, H. W., & Shohamy, E. (1989). Second language research methods. Oxford: Oxford
The coexsistance in the grammar of the schema and instantiations affords the speaker alternate ways of accessing a complex but regular expression with unit status: it can simply be activated directly, or else the speaker can employ the schema to compute it. Moreover, the schema is available for the computation of novel instantiations (e.g. quagmires); if such an expression is frequently employed, it may very well become established as a unit and thus be incorporated per se in the grammar. (Langacker 2002: 264)