[SciPy-User] approach used in special function iti0k0

I am searching for the approach/algorithm used to compute the special function iti0k0. The docs only state that the integrals \int_0^x I_0(t) dt and \int_0^x K_0(t) dt are computed, but I couldn't find a link/reference to the algorithm/approach used to compute these. Even iti0k0?? doesn't help. Anybody know? Thanks, Mark