[…] "θ-role assignment": (47) α is assigned the θ-role φ if and only if α or a trace "t" coindexed with α occupies a θ-position that is θ-marked φ, where "t" is not bound by an operator that fails to bind α.
- Chomsky (1993), a pag.116

[…] θ-role assignment is determined by the principle (18): (18) Suppose that the position "P" is marked with the θ-role "R" and C = (α1,..., αn) is a chain. Then C is assigned "R" by "P" if and only if for some "i", α"i" is in position "P" and C has Case or is headed by PRO.
- Chomsky (1993), a pag.334