Although it would be foolish to claim that every important parameter of rhetorical variation appearing over the last 300 years in the PTRS has been described in this chapter, each of the foregoing categories does reflect a major axis of change. It would be equally foolhardy to purvey this or any analysis of the PTRS as an objective and definitive description of the textworld in question; instead, the present analysis should be read

in conjunction with others that cover some of the same territory, such as Allen, Qin, and Lancaster (1994), Bazerman (1988, chap. 3), Dear (1985), Katzen (1980), Paradis (1987), and Valle (1997).