Found:

Chain Condition

**SYNTAX: **wellformedness condition on **chain**s, which states that every chain (a_{1},...,a_{n}) must contain exactly one Theta-marked position and exactly one Case-marked position. In A-chains a_{1} is Case-marked and a_{n} is Theta-marked, while in A'-chains the lowest **variable** A'-bound by the operator is Case-marked, and may either be Theta-marked, or A-bind a Theta-marked position in the chain. This condition restates the **case filter** (or the **visibility condition**) and the
**Theta criterion** in terms of chains.

LIT. | Chomsky, N. (1986b) Chomsky, N. (1986a) Chomsky, N. (1981) |