When reading squibs, some standard notations and abbreviations are used:

Abbreviation Translation A (B) C ABC or AC (i.e, B is optional)

A (*B) C AC is OK, ABC is bad (i.e, B is forbidden)

A *(B) C ABC is OK, AC is bad (i.e, B is necessary)

~ Not  A / ~ A A is necessary / A is not necessary ∃ A There is A / A is grammatical ~∃ A / ∄ A There is no A / A is ungrammatical (= *A) [I learned the latter meaning of this symbol from Zellig Harris]

# This symbol is used, in writing the structural description or change of a rule, to indicate that a node is Chomsky-adjoined to another.

Thus, if A immediately dominates B, Chomskyadjoining C to the left of A, will result in a structure with a new node A that immediately dominates C on the left, and also dominates the old node A on the right (which will continue to dominate B).