added some of the comments of the reviewers and made it compile with current Isabelle
(*
no_document use_thys ["This_Theory1", "This_Theory2"];
use_thys ["That_Theory1", "That_Theory2", "That_Theory3"];
*)
use_thy "ListP";
use_thys ["../Prefix_subtract", "../Myhill_1", "../Myhill_2"];