http://www.bbc.co.uk/worldservice/learningenglish/language/wordsinthenews/2014/07/140707_witn_elephants_story.shtml
trekking camps
In general, present and past participles can form non-finite clauses to modify a noun. The shortest form is the participle by itself, which is usually placed before a noun. If the participle has objects or adverbs, it is usually after the noun.
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