Observerare

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  Albert Etter

  https://ruuby.us/%EB%A8%B9%ED%8A%80%EA%B2%80%EC%A6%9D-%EB%B9%A0%EB%A5%B8-%EC%82%AC%EC%9D%B4%ED%8A%B8-%EC%95%88%EC%A0%84%ED%95%9C-%EC%98%A8%EB%9D%BC%EC%9D%B8-%EA%B2%8C%EC%9E%84-%ED%99%98%EA%B2%BD%EC%9D%84-%EC%9C%84/