Sicp isn't in there because it's almost a common noun on this forum by now. People don't link to the amazon page for it, just like they don't link to the bible :)
Hmmm, and I cite books a lot, but I often link to their Wikipedia page, since good ones can give the reader a better idea if one is worth reading, and they include ISBNs so it's really easy to find the exact book on Amazon (just search using the ISBN excluding the dashes).