When ν is fixed and z→0,
See also §10.24 when z=x (>0).
For H−ν(1)(z) and H−ν(2)(z) when ℜν>0 combine (10.4.6) and (10.7.7). For Hiν(1)(z) and Hiν(2)(z) when ν∈ℝ and ν≠0 combine (10.4.3), (10.7.3), and (10.7.6).
When ν is fixed and z→∞,
For the corresponding results for Hν(1)(z) and Hν(2)(z) see (10.2.5) and (10.2.6).