  These are notes of a seminar held at the Institute for Problems in Mechanics,
RAS in 2003 and aimed at presentation of [R.J. DiPerna and P.L. Lions, Invent.
math. 98, 511 (1989)]. We discuss the notion of a generalized solution to a
singular Ordinary Differential Equation introduced by DiPerna and Lions. We
stress importance of singular dynamic systems from the "philosophia naturalis"
point of view, and extend and simplify the original approach by R.J. DiPerna
and P.L. Lions. Further extensions are discussed.
