This is much better than the leakage article by the same authors, where they went on for ever without stopping to explain what "leakage" is. To this day, I have

This is much better than the leakage article by the same authors, where they went on for ever without stopping to explain what "leakage" is. To this day, I have no idea what, exactly, they meant. Reading their article now, I see that they say leakage is "roughly the same as contamination".