docs: def c_Duffy(z, m, h=h):
      """Concentration from c(M) relation published in Duffy et al. (2008).
  
      Parameters
      ----------
      z : float or array_like
          Redshift(s) of halos.
      m : float or array_like
          Mass(es) of halos (m200 definition), in units of solar masses.
      h : float, optional
          Hubble parameter. Default is from Planck13.
  
      Returns
      ----------
      ndarray
          Concentration values (c200) for halos.
  
      References
      ----------
      Results from N-body simulations using WMAP5 cosmology, presented in:
  
      A.R. Duffy, J. Schaye, S.T. Kay, and C. Dalla Vecchia, "Dark matter
      halo concentrations in the Wilkinson Microwave Anisotropy Probe year 5
      cosmology," Monthly Notices of the Royal Astronomical Society, Volume
      390, Issue 1, pp. L64-L68, 2008.
  
      This calculation uses the parameters corresponding to the NFW model,
      the '200' halo definition, and the 'full' sample of halos spanning
      z = 0-2. This means the values of fitted parameters (A,B,C) = (5.71,
      -0.084,-0.47) in Table 1 of Duffy et al. (2008).
      """
  
      z, m = _check_inputs(z, m)
  
      M_pivot = 2.e12 / h  # [M_solar]
  
      A = 5.71
      B = -0.084
      C = -0.47
  
      concentration = A * ((m / M_pivot)**B) * (1 + z)**C
  
      return concentration