If you’re interested in techniques for estimation, you should take a look at this pdf ebook. It contains half-a-dozen essays on estimating in agile projects, drawn from our experiences with a wide range of clients. We explain approaches based on story points and on story counting, which should give you a good overview for you to explore an approach that will work for you.
"How do you estimate on an Agile project?" by Martin Folwer and ThoughtWorks
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