Subset_FU_DU.txt

FU
  FU_{0,S,id,lim}
  FU_incr_seq
  FU_union_{finite,seq}
  FU_disj_{l,r}

DU
  DU_{equiv{,_def},0?,S?}
  DU_incl_seq_l
  DU_union_{finite{_incl{,'},},seq}
  DU_disj_{finite,seq}{,'}