Halliday & Matthiessen (2004: 554):
… there are two primary anaphoric strategies for tracking a referent as a text unfolds. The speaker or writer can use either (i) a personal reference item (personal pronoun or possessive determiner) or (ii) a specified noun. A ‘specified noun’ is either an inherently specific one — a proper noun — or else a common noun (serving as Thing) modified by a demonstrative determiner as Deictic.