We should only write on one side of these papers so that in searching through them, we do not have to take out a paper in order to read it. This doubles the space, but not entirely (since we would not write on both sides of all the slips). This consideration is not unimportant as the arrangement of boxes can, after some decades, become so large that it cannot be easily be used from one’s chair. In order to counteract this tendency, I recommend taking normal paper and not card stock.