Die Hamburger Sternwarte. ("The Hamburg Observatory"), Report on the Hamburg Observatory by R. Schorr, English Translation by Hamburg Observatory "Hamburger Sternwarte : History". Archived from the original on 2014-06-27. Retrieved 2014-10-01.
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Die Hamburger Sternwarte. ("The Hamburg Observatory"), Report on the Hamburg Observatory by R. Schorr, English Translation by Hamburg Observatory "Hamburger Sternwarte : History". Archived from the original on 2014-06-27. Retrieved 2014-10-01.