Chapter 66
Differential equations and the calculus of variations by L. ElSGOLTS. MIR PUBLISHERS, MOSCOW, Third printing 1977.

66.1 Chapter 1, First-Order Differential Equations. Problems page 88
66.2 Chapter 2, DIFFERENTIAL EQUATIONS OF THE SECOND ORDER AND HIGHER. Problems page 172
66.3 Chapter 3, SYSTEMS OF DIFFERENTIAL EQUATIONS. Problems page 209