Biographischer Index der Astronomie = Biographical index of astronomy / Wilhelm Brüggenthies,
Wolfgang R. Dick. - Frankfurt am Main : Deutsch, 2005
Information trouvée : Axel Vilfred Nielsen (1902-1970)
On the Variation of the Period of [êta] Aquilae/ by Axel V. Nielsen, ca 1931. - Tiré
à part de : "Astr. Nachr.", Bd 243, Nr 5832, Nov. 1931