The rules that use the category "<item_n-sing>" are:

<item>

<det-sing> <item_n-sing>

<det-sing> <item_n-sing> <location_mod>

<item-not_call_sign>

<det-sing> <item_n-sing>

<det-sing> <item_n-sing> <location_mod>

<new_item>

<up_to_thirty-sing> <item_n-sing>