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

<np-gapsout_null-gapsin_null-np_type_null-not_wh_or_dummy-sing>

<discourse_det-not_wh_or_dummy-sing> <n-sing-np_type_null>

<np-gapsout_null-gapsin_null-np_type_null-not_wh-sing>

<discourse_det-not_wh-sing> <n-sing-np_type_null>

<n-proper_name-unit> <poss> <n-sing-np_type_null>

<np-gapsout_null-gapsin_null-np_type_null-not_wh_or_gq_or_dummy-sing>

<discourse_det-not_wh_or_gq_or_dummy-sing> <n-sing-np_type_null>

<n-proper_name-unit> <poss> <n-sing-np_type_null>