Advanced Three Level Approximation for Numerical Treatment of   Cosmological Recombination
  New public numerical code for fast calculations of the cosmological recombination of primordial hydrogen-helium plasma is presented. The code is based on the three-level approximation (TLA) model of recombination and allows us to take into account some fine physical effects of cosmological recombination simultaneously with using fudge factors. The code can be found at http://www.ioffe.ru/astro/QC/CMBR/atlant/atlant.html 
Evgeny E. Kholupenko, Alexandre V. Ivanchik, Sergey A. Balashev,   Dmitry A. Varshalovich
astro-ph.CO