Harry Lorayne - How to Develop A Super-Power Memory
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The book is written in very simple language.It is pretty thin so it does not discourage you from reading it in case you don't have too much patience. I found it extremely useful in my final semesters of engineering when I was required to appear in exams which at times were just a few hours apart.The chain links and peg methods were very useful and allowed me to remember important points and numbers,many of which I had studied more than a month before by exams .Just a last minute glance at the pegs was enough to allow me to recollect all the data on the subject.