Conditions of Use

All contents on are copyrighted. If you would like to use any content on, please follow the rules below:

  1. If your use is for noncommercial purposes, either (a) cite the site by including both “XY” and “” in your citation or (b) contact us at for clarification;
  2. If your use is for commercial purposes, you need to contact us at;
  3. If your use is for both commercial and noncommercial purposes, refer to rule (2).