sS simpleWikipedia_cached(S topic) {
  File f = javaxDataDir("Simple Wikipedia Pages", uniqueFileNameUsingMD5_80(topic));
  if (fileExists(f)) ret loadTextFile(f);
  S page = loadPage("https://simple.wikipedia.org/wiki/" + topic.replace(" ", "_")  + "?action=raw");
  saveTextFile(f, page);
  ret page;
}