Martin (1992: 575):
Halliday himself it should be noted has remained rather Firthian in character as far as semantics is concerned, preferring register specific descriptions and cautioning against premature attempts to describe the semantic system as a whole — e.g. 1988: 3; needless to say English Text has nowhere heeded this caution.
 The SFL model of ideational semantics is set out in Halliday & Matthiessen (1999).
 This is true.