Halliday & Matthiessen (1999: 118):
The following passage of spontaneous conversation exemplifies the principal categories of expansion (note than it also contains one example of projection):
KEY: parataxis [equal]: 1, 2; hypotaxis [unequal]: 𝛂, 𝛃); elaboration: =; extension: +; enhancement: x. (Taken from Svartvik & Quirk, 1980:430.)