John Neville Keynes 
Studies and Exercises in Formal Logic [PDF ebook] 
Including a Generalization of Logical Processes in Their Application to Complex Inference

Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. Points of theory have received considerable develop ment. Throughout the book the unanswered exercises are now separated from the expository matter and placed together at the end of the several chapters in which they occur. An index has been added.