Complex sentence: This core idea was developed further by Kenneth R. Andrews in 1963 into what we now call SWOT analysis, in which the strengths and weaknesses of the firm are assessed in light of the opportunities and threats in the business environment.
Split into simpler sentences: This core idea was developed into what we now call SWOT analysis. Strengths and weaknesses of the firm are assessed in light of the opportunities and threats in the business environment.