Complex sentence: The test was developed in 1927 by psychologists E.K. Strong, Jo-Ida Hansen, and David Campbell based on the typology (Holland Codes) of psychologist John L. Holland.
Split into simpler sentences: The test was developed in 1927 by psychologists E.K. Strong, Jo-Ida Hansen, and David Campbell. The modern version is based on the typology (Holland Codes) of psychologist John L. Holland.