Milton Rokeach's "The Nature of Human Values" (1973) defines values as enduring beliefs, categorizing them into terminal (desired end-states) and instrumental (preferred behaviors) systems. The work introduces the Rokeach Value Survey (RVS) to measure these 36, or 18 in each category, values, asserting they are finite, hierarchically organized, and predictive of behavior. You can access a summary of Rokeach's values survey on (PDF) Rockeach Values - Academia.edu

Rokeach’s most enduring contribution is the distinction between two specific types of values that make up an individual's "value system": Milton Rokeach's Experimental Modification of Values

Measurement: the Rokeach Value Survey (RVS)

Rokeach developed the Rokeach Value Survey to measure value priorities. The RVS lists 18 terminal and 18 instrumental values and asks respondents to rank them in order of importance. Key features: