{
  "title": "Natural Numbers and Commutativity of Addition",
  "origin_url": "http://matita.cs.unibo.it/gitweb/?p=helm.git;a=blob;f=matita/matita/lib/tutorial/chapter2.ma",
  "license_guess": "GPL-2.0",
  "code_sha256": "1b897b70dc1d6fa86dec8321451117ab1155aabd23dfa535bf13bf00b0218ec4",
  "added_at": "2026-02-10T13:36:50Z"
}