Martin (1992: 119-20):
The second way of avoiding the reference systems outlined above is to use [generalised] reference (Halliday & Hasan 1976: 53-54). … The relationship of these "out" options to the principal reference systems is formulated systemically in Fig. 3.9. For more delicate realisations of the features [presenting], [undirected] and [comparison] see the networks presented in the course of the description above.
 To be clear, as Halliday & Hasan (1976: 53-4) point out, this is generalised exophoric reference, and as such, makes no contribution to the cohesion of a text. More importantly, Martin violates the principle of stratification by relocating Halliday & Hasan's generalised reference from lexicogrammar to his own discourse semantics, without regard to the different levels of symbolic abstraction that the strata represent.
 This strategically confuses two distinct dimension of SFL theory, delicacy and realisation. More delicate features are not realisations of less delicate features. Systemic delicacy is a scale of generality (intensive attribution) at one level of symbolic abstraction (stratum), whereas realisation is a relation (intensive identification) between two levels of symbolic abstraction, as between strata, or between axes, or between function and form; see e.g. Halliday & Matthiessen (1999: 144-5). The confusion is strategic because it falsely implies that Martin has specified how these features are realised.