[…] β is “closer to” HP than α if β c-commands α and is not in the minimal domain of CH, where CH is the chain headed by γ, γ adjoined within the zero-level projection H(K)°max. - Chomsky (1995), a pag.355
[…] "close" is (tentatively) defined in terms of c-command and equidistance. - Chomsky (1995), a pag.296