People in Greenland can differentiate between 36 kinds of snow; the Swedish International Master Ari Ziegler will teach you to differentiate between 20 kinds of exchange sacrifice. His systematic approach to exchange sacrifices will rapidly enhance your understanding of one of the most exciting and difficult aspects of chess. Your widened horizon will help you to be able to follow the games of top GMs better and also to see more options in your own positions, which in turn will improve your chess res