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Published online by Cambridge University Press: 04 August 2017
By comparison of U and B plates of M33 we extended the numerations of Humphreys and Sandage (1980) adding 54 new OB associations. The associations identified by HS are outlined with continuous line and ours are represented with dash on Figure 1. Many of the identified by us associations are near the nucleus of M33. Due to U plate used by us the background in the central region is fainter than that on the B plate and the associations are distinguished very well on U plate (Kunchev and Ivanov, 1984). Our associations of the outer region of M33 consist mainly of relatively fainter young B stars.