Chapter 20
Differential equations with applications and historial notes, George F. Simmons. Second edition. 1971

20.1 Chapter 2, section 7, page 37
20.2 Chapter 2, section 8, page 41
20.3 Chapter 2, section 10, page 47
20.4 Chapter 2, section 11, page 49
20.5 Chapter 2, End of chapter, page 61