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Since I don't know how deep in the TipiαΉaka's structure you want the answer, I'll try to give the most in-depth answer. I'll present the structure in a tree chart and, beneath it, I'll refer to an article with an in-depth analysis of the canon which provides the summaries.
(Click to enlarge)
Summaries are provided in "Chapter I: Textual Analysis of the article "An Analysis of the PΔαΈ·i Canon" by Russell Webb. It also contains an excellent index of the canon, and an extensive bibliography.