39.4 Chapter 12. VARIATION OF PARAMETERS. Supplementary Problems. page 109

39.4.1 problem Problem 12.9
39.4.2 problem Problem 12.10
39.4.3 problem Problem 12.11
39.4.4 problem Problem 12.12
39.4.5 problem Problem 12.13
39.4.6 problem Problem 12.14
39.4.7 problem Problem 12.15
39.4.8 problem Problem 12.16