Imagine that you would like to learn a few things about Gamal Abdel Nasser. You will, for example, import to SuperMemo an article about Nasser from Wikipedia. In the first sentence you will find out that "Gamal Abdel Nasser (1918 - 1970) was the second President of Egypt". If you are new to Nasser, you may be happy to just know he was the Egyptian president and safely jump to reading other articles. Thus you may delay the encounter with the historic role of Nasser and economize some time to finding out, for example, who Shimon Peres is. When you see the Nasser article for the second time, you might find that "He was followed by after President Muhammad Naguib and can be considered one of the most important Arab leaders in history". This piece of knowledge is also self-contained and you can patiently wait for your third encounter with Nasser. When you return the next time, you may conclude that another piece about Nasser is of lower priority: "Nasser was born in Alexandria". You can schedule the review of that piece in 2-3 years. Perhaps your interest in Nasser or in Alexandria will grow to the point that this knowledge will become relevant. If not, you can always dismiss or delete such an extract. Alternatively, you can skip a few paragraphs and extract a more important sentence: "In 1952, Nasser led the military coup against King Farouk I of Egypt". Even if your read individual sentences about Nasser in intervals lasting months, your knowledge will progressively expand and will become increasingly consolidated (esp. if you employ cloze deletions, which are mandatory for longer intervals).