  Charge radii of Sn, Ba, Yb, and Pb isotopes are calculated within
Hartree-Fock-Bogoliubov theory with a Skyrme force and a density-dependent
delta-force pairing. We investigate mean field effects of the pairing upon
odd-even staggering of isotope shifts. HFB equations are solved in the
canonical basis. Odd nuclei are treated in the blocking approximation.
