On the necessity for spectral sub-classification, with a discussion of preliminary results for 1300 southern stars
By: Dorrit Hoffleit
Series: Harvard reprint -- 177
Publisher: Astronomical Observatory of Harvard College
Published: 1939
Place of publication: Cambridge, Mass
Language: eng
Number of pages: 545
Notes: Proceedings of the American Philosophical Society, Vol. 81, No. 4, September, 1939."

Includes bibliographical references.