Here are a few highlights from Ch. 2 of Vachek, Josef. 1973. Written Language: General Problems and Problems of English. The Hague: Mouton.
Valchek sees a "momentous step" forward when Artymovyc "claims for written language a status to a degree independent of that of spoken language." p. 14.
Indeed, Vachek says, the appropriate enquiry is to try to find out the functional justification of the existence of written language. p. 15. "The written norm of language has its functional justification alongside the spoken norm: in some specific situations the former can serve the communicative needs of the members of a community better than the latter." p. 16.
The two norms, Vachek says, appear to be functionally compementary: one or the other will be found more appropriate to use in a given situation. p. 16
Vachek's Definition of Written Language
The Three Topical Progressions
How to Diagram Topical Progressions