Halliday & Matthiessen (2014: 610):
Cohesive conjunctions may be used within clause complexes, as in||| Someone comes along with a great idea for an expedition || – for example, I did a book called Sand Rivers, just before the Indian books, || and it was a safari into a very remote part of Africa. |||
But their real cohesive contribution is made when they are used to indicate logico-semantic relations that extend beyond the (grammatical) domain of a single clause complex. They may mark relations that obtain between two clause complexes, as in:
||| Taiwan’s newly elected leader expressed interest Friday in considering a confederation with rival China – a relationship a visiting Chinese policy expert said Beijing would surely reject. ||| Meanwhile, a list of top Cabinet members in Taiwan’s new government was announced, featuring prominent numbers of women, technocrats and academics who will be key in the push to improve relations with China and clean up corruption. |||
The relation may, in fact, even link to part of an earlier clause complex, as in:||| Given the demanding pace of military operations, || service members should be allowed to focus on their mission free from worry about the welfare of their families. ||| Accordingly, funding for quality DOD schools, child development activities, and other family assistance programs is important, particularly today || when the stresses of operational deployments are higher than ever before. |||
But the relation may also link domains that are more extensive than single clause complexes;