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Andersen, T.; Andersen, T.; Larsen, O. B.; Owner-Petersen, M.; Steenberg, K. (April 1992). Ulrich, Marie-Helene (ed.). Active Optics on the Nordic Optical Telescope. ESO Conference and Workshop Proceedings. Progress in Telescope and Instrumentation Technologies. pp. 311–314. Bibcode:1992ESOC...42..311AArxivləşdirilib 2022-03-23 at the Wayback Machine