Martin (1992: 405):
At this stage however all that needs to be stressed is that contextual systems are a critical component of any culture's text forming resources. The notion of text cannot be understood unless linguistic text forming resources are interpreted against the background of (or better, as redounding with) contextual ones.
 In SFL theory, contextual systems are not a component of a culture's text forming resources. Contextual systems model culture as a semiotic system, and do so in terms of all metafunctions: ideational (field), interpersonal (tenor) and textual (mode). The 'text forming resources', on the other hand, are linguistic systems of the textual metafunction.
 The 'linguistic text forming resources' — those of the textual metafunction — realise the system of mode, the textual dimension of context.
 To be clear, the meaning of 'redound' here — previously quoted from Halliday in Thibault (1987: 619) — is 'construes and is construed by'. So a theoretically consistent interpretation would be that the text forming resources construe and are construed by the contextual system of mode.