This opening book by the German master Bücker proposes hypermodern defense concepts against 1. d4 with 1…c5 2. d5 Nf6 3. c4 Ne4 (the Vulture), 3. Nf3 c4 (the Hawk), or 3.Nc3 Qa5 (the Woozle). While perhaps not entirely optimal, these are excellent weapons in rapid and blitz chess. The book is in German language, but is easily read using the Google Translate app on your smart phone. Many diagrams and complete games augment the analysis. Most of your opponents will have never seen these opening moves before, and you will gain an enormous time advantage on the clock.