These were stored in files. There are 38 sheets in total. They summarize standard techniques for difficult problems often seen in challenging university entrance exams, such as the introduction of corner variables. I think the level is similar to that of "Advanced Problem Solving". It seems like it would be good to study these in conjunction with materials like Sundai's selection for high school years 2 and 3 mathematics, Mathematics XS/ZS, Mathematics XZS, and the high school years 2 and 3 confirmation series from Teiryo-kai. Questions are welcome.