Sometimes they are changing their URLs for their site, and the old ones still work for a while, I suspect. I include all URLs for a site that I find so that at least one will work. This way you can get to the site without waiting for me to learn that the old one has vanished. The same page exists at more than one site. I include all of the URLs due to the volatility of the Net, so that the document will be available even if one page vanishes.
Similar pages exist at different sites.
In this case, the pages referred to are different pages about the same topic, and are merely grouped together for convenience. By the way, there are a few links you will not find here. There are no direct links to radio modification files. Such things put us in an awkward position with the authorities, as the manufacturers insist on making equipment that is easily modified for illegal operation. As a result, the relationship between the authorities and amateur radio dealers is always a bit strained.