BESSELI, BESSELJ, BESSELK, and BESSELY do have no example at all.
Moreover I do not understand the difference as reader between these 4 functions (actually all have the same explanation)
See also Apple's help and examples on
(the other two functions are not implemented by Apple)
A general idea: should we add Wikipedia links to Bessel?
Olivier Hallot committed a patch related to this issue.
It has been pushed to "master":
tdf#103431 HELP Bessel functions need examples