https://www.justinmath.com/individualized-spaced-repetition-in-hierarchical-knowledge-structures/ A common criticism of spaced repetition is that it requires an overwhelming number of reviews. While this can be true if spaced repetition is used to learn unrelated flashcards, there is something special about the subject of mathematics that can be used to avoid this issue.
Unlike independent flashcards, mathematics is a hierarchical and highly connected body of knowledge. Whenever a student solves an advanced mathematical problem, there are many simpler mathematical skills that they practice implicitly. In other words, in mathematics, advanced skills tend to encompass many simpler skills.
Интересное наблюдение про разбиение сложной задачи на простые и их совместное решение.