One of us has previously assertedMichael Nielsen, Augmenting Long-Term Memory (2018). that in spaced-repetition memory systems, users need to make their own cards. The reasoning is informal: users often report dissatisfaction and poor results when working with cards made by others. The reason seems to be that making the cards is itself an important act of understanding, and helps with committing material to memory. When users work with cards made by others, they lose those benefits.