On Second Order Linear Differential Systems

Consider the second order matrix differential system (1.1) X ″ ( t ) + A ( t ) X = 0 ,   t ≥ t 0 , https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003067498/6ba0c26b-f086-40cc-86ed-1693dc596221/content/eq350.tif"/>