doc-src/IsarImplementation/Thy/ROOT.ML

replace lemma realpow_two_diff with new lemma square_diff_square_factored

use_thys [
  "Integration",
  "Isar",
  "Local_Theory",
  "Logic",
  "ML",
  "Prelim",
  "Proof",
  "Syntax",
  "Tactic"
];