1. Delay-feedback solution for the minimal-time linear problem with several outputs;Asner;Rev. Roumaine Math. Pures Appl.,1973
2. Noncontrollability of time-invariant linear systems using one-dimensional linear delay feedback;Asner;Rev. Roumaine Sci. Tech. Ser. Électrotechnique et Énergétique,1973
3. Équations Différentielles avec Retard: Applications de la Dégénérescence à la Théorie de la Commande;Charrier,1972
4. F. Kappel, Some remarks to the problem of degeneracy for functional differential equations, private communication.
5. Pointwise degeneracy of linear, time-invariant, delay-differential equations;Popov;J. Differential Equations,1972