»The reference book Who Knows What listed Hartman as one of the two living authorities on value theory (the other was Charles W. Morris (1903-1979). Among Hartman's publications are the report on Value Theory for the Institut International de Philosophis 1949-1955, published by UNESCO; his magnum opus The Structure of Value (1967 Southern Illinois University Press); and at the time of his death in 1973 he was working on a manuscript entitled The Measurement of Value.«
See also https://archive.org/details/structureofvalue0000robe