Passbooks: - National Learning Corporation has been a leading publisher of test-preparation Passbooks(R) for more than 50 years, with 6,000 titles available across 22 series. The DSST (Defense Activity for Non-Traditional Education Support) Subject Standardized Tests are comprehensive college and graduate level examinations given by the Armed Forces, colleges and graduate schools. These exams enable students to earn college credit for what they have learned through self-study, on the job, or by other non-traditional means. Each book in the DSST Series offers practice through multiple-choice questions and answers in relevant subject areas, as well as informative texts to aid in understanding the study material.