The rules that use the category "<existence_claim-pl-inv-gapsout_null-gapsin_np_gap>" are:
<np-gapsout_null-gapsin_null-wh-pl> <existence_claim-pl-inv-gapsout_null-gapsin_np_gap>
<np-gapsout_null-gapsin_null-wh-pl> <existence_claim-pl-inv-gapsout_null-gapsin_np_gap>