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

<unit-gapsout_null-gapsin_null-sing>

<det-sing-def> <unit_nom-not_det-sing>

<unit-gapsout_null-gapsin_null>

<det-sing-def> <unit_nom-not_det-sing>

<line_loc-gapsout_null-gapsin_null>

<det-sing-def> <line_type>