We link pretty liberally right now, because we can. I'd like to know from nostarch:

• I'm assuming we should prefer "see Chapter XX" for in-book references?
• Should we link to the API docs when we mention something in the standard library?
  • Maybe only the first time we reference something?
  • And for print the links should be absolute, right? Should links to API docs be absolute or relative? #131
• Should links be inline like the links to unicode.org here? Or footnotes? https://github.com/rust-lang/book/blob/first-third-try/src/ch03-02-data-types.md#the-character-type
• Should we be thinking about the likelihood of the content we're linking to going away? That is, unicode.org likely isn't going to disappear anytime soon, but something like, say, http://cglab.ca/~abeinges/blah/too-many-lists/book/ might, or change URLs (didn't he graduate???)