ABSTRACT
We present Ekeland’s variational principle to give a simple proof to the maximum principle of time-delay system () { d x ( t ) / d t = f [ t , x ( t ) , x ( t − θ ) , u ( t ) ] x ( t ) = φ ( t ) , t 0 − θ ⩽ t ⩽ t 0 and x ( t 1 ) = x 1 } https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003067498/6ba0c26b-f086-40cc-86ed-1693dc596221/content/eq2372.tif"/>
