Postmodification by nonfinite clauses
Postmodification by -ing participle clauses
17.28 Postmodification of the noun phrase is possible with all three of the nonfinite clause types: -ing participle, -ed participle, and infinitive clauses. The correspondence between -ing clauses and relative clauses is limited to those relative clauses in which the relative pronoun is subject:
will be writing
The person who writes reports is my colleague. 
The person writing reports is my colleague. [1a]
The nonfinite clause "writing reports" in [1a] may be interpreted, according to the context, as equivalent to one of the more explicit versions in .
It must be emphasised that -ing forms in postmodifying clauses should not be seen as abbreviated progressive forms in relative clauses. Stative verbs (e.g. occur), for instance, which cannot have the progressive in the finite verb phrase, can appear in participial form.