Standard Cell Libraries (Basic)

Dear Sirs.

I want to make my little Standart Cell library.
I want that in my library there must have been not only gates but also triggers.
How to choose the necessary and sufficient set of standard cells for a standart cell library?
By what principle is the selection of cells? (It is clear that there is a variation of _X1, _X2, ...)
How to determine the size of transistors in cells? Align the delay on the 0->1, 1->0 or the rise time, the fal time?

If possible, advise literature on this issue.

Thanks.

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