A set of textbooks and problem books that clearly explains the theory of Denken San-shu (3rd class electrical engineer). - Title: Denken San-shu Theory Textbook & Problem Book - Publisher: TAC Publishing - Edition: 2nd Edition - Features: Easy-to-understand textbook - Contents: Problem book related to the theory of Denken San-shu Thank you for viewing. I am selling this because I passed the exam. Overall, there are folds, bends, and tears, and there are writings in the problem book, so there is a strong feeling of use, but I think there is no problem with readability. Please purchase only if you understand that this is a used item. The problem book and textbook have been separated and will be shipped disassembled and with the covers compressed due to thickness.