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Analytic methods give powerful tools for obtaining asymptotic estimates in combinatorial enumeration. When they can be used، نويسنده , , they usually provide extremely precise results. However، نويسنده , , there are also many situations where they do not apply، نويسنده , , and one has to use elementary or probabilistic reasoning. Problems in various classes are presented، نويسنده , , and general principles of what kinds of methods are best for various situations are discussed.، نويسنده ,