Can mild anaemia increase the risk of complications in patients over 65 years of age compared to younger patients undergoing cardiac surgery? - Kowalczuk-Wieteska, Anetta M.; Majchrzyk, Iwona; Zembala, Marian; Zembala, Michał (Advances in Interventional Cardiology/Postępy w Kardiologii Interwencyjnej, 2020)