  A comparative analysis has been done of the formerly established two
self-consistent solutions for the density of quasiparticle states in doped
d-wave superconductors, having strikingly different and disputed behavior near
the Fermi energy. One of them (1) remains finite in this limit, while the other
(2) tends to zero. To resolve this discrepancy, the known Ioffe-Regel criterion
for band states, widely used for doped semiconductors, was applied to these
solutions. It is shown that both them are valid in limited and different energy
regions, where the corresponding quasiparticles are weakly damped. In
particular, density of states of nodal quasiparticles near the Fermi level is
provided by the (2) solution, while the (1) only applies far enough from this
level.
