[1] C. CARATHÉODORY: Vorlesungen über reelle Funktionen. Leipzig 1927.
[2] O. HÁJEK: 
Theory of processes I. Czech. Math. Journal (to appear). 
MR 0212311[3] K. KARTÁK: 
A generalization of the Carathéodory theory of differential equations. Czech. Math. Journal (to appear). 
MR 0220998