Complex sentence: The theoretical foundations of the MBTI and DiSC approaches were eveloped in the 1920s and the "Briggs-Myers Type Indicator" was first published in 1942.
Split into simpler sentences: The theoretical foundations of the Meyers-Briggs Personality Type Indicator ® (MBTI ®) and the DiSC assessment were developed in the 1920s. The "Briggs-Myers Type Indicator" was first published in 1942.