Contributions to the photographic study of colour, resolution and total magnitude of anagalactic objects : with special regard to objects photographed at Helwan / Bjorn Svenonius. Svenonius, Bjorn. Observatories. 522.1 SVC Lund : Observatory, c1938. c1938. 1938 Text 160 p.: eng Annals of the observatory of Lund; no. 7.