abbreviation for Advanced Clinical Course: one of a number of theory and research courses delivered by L. Ron Hubbard during the years 1953 to 1961, which gave a deep insight into the phenomena of the mind and the rationale o f research and investigation. In this lecture, Ron is referring to the HCO Special Events Course which started 3 July 1961 in Washington, DC, and was delivered by auditors who had arrived from training at Saint Hill. Rudiments, Valences Approved April 1991