Explore a conference talk on spaces of quasi-invariants delivered by Yuri Berest at the Centre International de Rencontres Mathématiques in Marseille, France. Delve into complex reflection groups, multiplicity functions, and quasi-invariants, examining their elementary properties and algebraic characteristics. Discover the connections between these concepts and their applications in elliptical homology. Gain insights into the motivations behind this research and potential generalizations. Access this video and other mathematical talks through CIRM's Audiovisual Mathematics Library, featuring chapter markers, keywords, abstracts, and a multi-criteria search function for enhanced navigation and comprehension.