Non-Unique Critical Points of Ordinary Differential Equations. - Stephen R. Bernfeld (Math. Syst. Theory, 1972)

Uniqueness For Ordinary Differential Equations. - Stephen R. Bernfeld; Rodney D. Driver; V. Lakshmikantham (Math. Syst. Theory, 1976)

Differential Equations with Discontinuous Righthand Sides (A. F. Filippov). - Stephen R. Bernfeld (SIAM Rev., 1990)