We are grateful to A.Y. Potekhin for providing us with the program which calculates the electron chemical potential. Two of the authors (VGB and ADK) acknowledge excellent working conditions and hospitality of N. Copernicus Astronomical Center in Warsaw. This work was supported in part by KBN (grant 2P 304 014 07), RBRF (grant No. 96-02-16870a), INTAS (grant No. 94-3834), and DFG-RBRF (grant No. 96-02-00177G).
© European Southern Observatory (ESO) 1997
Online publication: March 24, 1998