This book is the third and final volume in a series entitled "The Modula-2 Software Component Library." C. Lins' collection of reusable standard software components could be the basis for every programmer's software project in Modula-2. Components that are implementations of commonly used data structures are presented, along with a description of their functionality and efficiency. Moreover, the books provide the background necessary to tailor these components to the specific needs of any Modula-2 environment. For Modula-2 programmers, this series of books could prove as useful and indispensible as the original language reference by Niklaus Wirth. This third volume discusses the concepts of trees and graphs, shows their specifications, and provides implementations for various forms of trees and graphs.