Martin (1992: 392):
As far as lexical strings and reference chains are concerned, this interaction across strata is better understood than that among discourse systems themselves. Fries (1981), Hasan (1984), Halliday (1985) and Plum (1988) have all done pioneering work in this area (see also Martin 1991).
To be clear, in SFL theory, the cohesive relations effected by lexical cohesion and reference are located at the level of lexicogrammar and within the textual metafunction. Studies that examine how the non-structural systems of the lexicogrammar pattern with the structural systems of the lexicogrammar are thus not concerned with "interaction across strata".
To be clear, in discourse semantic theory, lexical strings are construed as experiential structures at the level of discourse semantics, and reference chains are construed as textual structures at the level of discourse semantics.
Accordingly, the work of Fries (1981), Hasan (1984) and Halliday (1985) does not support the relocation of non-structural textual systems at the level of lexicogrammar to structural experiential and textual systems at the level of discourse semantics.