Found:
Angled brackets
PHONOLOGY: a notational convention used to collapse rules. EXAMPLE: the two rules (i) and (ii) can be collapsed as (iii).
(i) A -> B /_____Y X Z (ii) A -> B /_____Y Z (iii) A -> B /_____Y <X> ZThe difference between the rules (i) and (ii) is the presence or absence of the variable X.
| LIT. | Chomsky, N. and M. Halle (1968) |