Thomas, David A., and Emily Heaphy. "Personality Types: The Myers-Briggs Type Indicator (TN)." Harvard Business School Teaching Note 498-069, March 1998.

Based on the results of MBTI questionnaires, individuals are classified as one of 16 personality types consisting of combinations of the above—e.g., INFP (Introvert, Intuitive, Feeling, Perceiving).