4a5
+ *] http://strongloop.com/strongblog/node-js-callback-hell-promises-generators/
3a4
+ *] http://blog.gvm-it.eu/post/22040726249/callback-conventions-in-node-js-how-and-why
2a3
+ *] http://book.mixu.net/node/
0a1,2
+ Nützlich:
+ *] https://www.joyent.com/developers/node/design/errors