function Space1999(disc) {
  if(isNaN(disc)) {
    disc = 0;
  }
  if(disc != 0) {
    document.write("<h2>The Other Episodes</h2>");
  }
  if(disc != 1) {
    document.write("<a href='space_1999_1.htm'>Space: 1999, Volume 1</a><br>");
  }
  if(disc != 2) {
    document.write("Space: 1999, Volume 2<br>");
  }
}