Lateral autocorrelation function of roughness is used inconsistently

In Sample/Interface/LayerRoughness.cpp there are functions

double LayerRoughness::spectralFunction(const R3 kvec) const

and

double LayerRoughness::corrFunction(const R3 k) const

spectralFunction should be two-dimensional Fourier transform of the correlation function.

Since we have spectralFunction in form:

the correlation function should be

But instead of using (A2) corrFunction represents (A1):

Formulas are taken from

D.K.G. de Boer, Physical review B, Volume 51, Number 8, 15 February 1995 "X-ray reflection and transmission by rough surfaces", Appendix A