1967. Fourth edition. 166 pages. This is an ex-Library book. Laminated pictorial dust jacket over brown cloth. Black and white diagrams throughout. Ex library copy with associated labels, inserts, stamps and annotations. Pages remain bright and clean with minimal tanning and foxing. Binding remains firm. Boards assumed in good condition as covered with library laminated jacket. Unclipped jacket has light edge wear with minor chipping and creasing. Some tanning and foxing to all surfaces, particularly to spine.