In this paper we study the approximate positive controllability and positive observability of linear systems. The characterization of the above concepts is given. The duality between the approximate positive controllability and positive observability is obtained. Necessary and sufficient conditions are formulated and proved. The abstract results are illustrated by several examples.
"Approximate Positive Controllability and Positive Observability for Standard Linear Systems." Commun. Math. Anal. 17 (1) 57 - 66, 2014.