[...] α c-commands β if and only if (i) α does not contain β; (ii) suppose that γ1,..., γn is the maximal sequence such that (a) γn = α, (b) γi = αj, (c) γi immediatly dominates γi+1. Then if δ dominates α, then either (I) δ dominates β, or (II) δ = γi and γ1 dominates β. - Chomsky (1993), a pag.166