The BESSEL functions, -I, -J, -K, -Y, share:

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Returns: Number

Constraints: N >= 0, INT (N)=N; Evaluators may evaluate expressions where N >= 0 returns a non-error value.

Semantics: .... N is also known as the order.

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Should there be a general section that summarizes what is common among BESSEL functions and leaves varying details to the individual entries? 

If we say yes, I will create separate Jira issues for each of the Bessel functions with their required edits.