Obserwujący

• 

  Jerri Stillings

  https://math96.angelinsblog.com/31491025/%ea%b2%8c%ec%9e%84-%ed%94%8c%eb%9e%ab%ed%8f%bc-%ea%b0%80%ec%9e%85-%ec%8b%9c-%ed%99%95%ec%9d%b8%ed%95%b4%ec%95%bc-%ed%95%a0-%ed%95%84%ec%88%98-%ec%82%ac%ed%95%ad